|
Real Estate and Intangible Assets - Schedule of Revenue and Earnings Recognized on Properties Acquired (Detail) (USD $)
In Thousands, unless otherwise specified
|
12 Months Ended |
|
Dec. 31, 2014
|
Dec. 31, 2013
|
| Business Acquisition [Line Items] |
|
|
| Rental Revenue |
$ 5,605good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
|
$ 5,155good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
|
| Earnings |
2,492good_NetIncomeLossFromAcquiredProperties
|
1,981good_NetIncomeLossFromAcquiredProperties
|
| Allen, TX [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Mar. 27, 2014
|
Jul. 10, 2013
|
| Rental Revenue |
435good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AllenTxMember
|
685good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AllenTxMember
|
| Earnings |
249good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AllenTxMember
|
300good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AllenTxMember
|
| Colleyville, TX [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Mar. 27, 2014
|
|
| Rental Revenue |
357good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_ColleyvilletxMember
|
|
| Earnings |
206good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_ColleyvilletxMember
|
|
| Rancho Cordova, CA [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Apr. 22, 2014
|
|
| Rental Revenue |
625good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_RanchoCordovaCaliforniaMember
|
|
| Earnings |
239good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_RanchoCordovaCaliforniaMember
|
|
| Coppell, TX [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
May 08, 2014
|
|
| Rental Revenue |
390good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_CoppelltxMember
|
|
| Earnings |
226good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_CoppelltxMember
|
|
| Columbus, OH [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
May 13, 2014
|
|
| Rental Revenue |
790good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_ColumbusOHMember
|
|
| Earnings |
272good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_ColumbusOHMember
|
|
| Taylor, PA [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Jun. 09, 2014
|
|
| Rental Revenue |
1,908good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_TaylorpaMember
|
|
| Earnings |
890good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_TaylorpaMember
|
|
| Aurora, CO [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Jul. 01, 2014
|
|
| Rental Revenue |
384good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AuroraMember
|
|
| Earnings |
253good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AuroraMember
|
|
| Indianapolis, IN [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Sep. 03, 2014
|
|
| Rental Revenue |
489good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_IndianapolisMember
|
|
| Earnings |
44good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_IndianapolisMember
|
|
| Denver, CO [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Oct. 31, 2014
|
|
| Rental Revenue |
166good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_DenverCoMember
|
|
| Earnings |
82good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_DenverCoMember
|
|
| Egg Harbor Township, NJ [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
|
Mar. 28, 2013
|
| Rental Revenue |
|
373good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_EggHarborTownshipNjMember
|
| Earnings |
|
209good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_EggHarborTownshipNjMember
|
| Vance, AL [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
|
May 09, 2013
|
| Rental Revenue |
|
757good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_VanceAlMember
|
| Earnings |
|
363good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_VanceAlMember
|
| Blaine, MN [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
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May 10, 2013
|
| Rental Revenue |
|
947good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_BlaineMnMember
|
| Earnings |
|
424good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_BlaineMnMember
|
| Austin, Texas [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
|
Jul. 09, 2013
|
| Rental Revenue |
|
2,299good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AustinTxMember
|
| Earnings |
|
655good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_AustinTxMember
|
| Englewood, CO [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
|
Dec. 11, 2013
|
| Rental Revenue |
|
85good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_EnglewoodCoMember
|
| Earnings |
|
25good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_EnglewoodCoMember
|
| Novi, MI [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
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Dec. 27, 2013
|
| Rental Revenue |
|
9good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_NoviMiMember
|
| Earnings |
|
5good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_NoviMiMember
|
| Monroe, MI [Member] |
|
|
| Business Acquisition [Line Items] |
|
|
| Acquisition Date |
Dec. 23, 2014
|
|
| Rental Revenue |
61good_OperatingLeasesIncomeStatementLeaseRevenueFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_MonroeMember
|
|
| Earnings |
$ 31good_NetIncomeLossFromAcquiredProperties
/ us-gaap_BusinessAcquisitionAxis
= good_MonroeMember
|
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