Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Future Minimum Rental Payments Due under Terms of Leases (Detail)

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Commitments and Contingencies - Future Minimum Rental Payments Due under Terms of Leases (Detail) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended
Jun. 30, 2014
Operating Leased Assets [Line Items]  
For the year ended December 31, 2014 $ 34,255
For the year ended December 31, 2015 63,228
For the year ended December 31, 2016 62,763
For the year ended December 31, 2017 61,125
For the year ended December 31, 2018 61,469
Ground Leases [Member]
  
Operating Leased Assets [Line Items]  
For the year ended December 31, 2014 206
For the year ended December 31, 2015 413
For the year ended December 31, 2016 413
For the year ended December 31, 2017 416
For the year ended December 31, 2018 417
For the year ended December 31, 2019 417
Thereafter 4,501
Ground Leases [Member] | Tulsa, OK [Member]
  
Operating Leased Assets [Line Items]  
Lease End Date 2021-04
For the year ended December 31, 2014 76
For the year ended December 31, 2015 153
For the year ended December 31, 2016 153
For the year ended December 31, 2017 153
For the year ended December 31, 2018 153
For the year ended December 31, 2019 153
Thereafter 229
Ground Leases [Member] | Dartmouth, MA [Member]
  
Operating Leased Assets [Line Items]  
Lease End Date 2036-05
For the year ended December 31, 2014 87
For the year ended December 31, 2015 174
For the year ended December 31, 2016 174
For the year ended December 31, 2017 174
For the year ended December 31, 2018 174
For the year ended December 31, 2019 174
Thereafter 3,300
Ground Leases [Member] | Springfield, MA [Member]
  
Operating Leased Assets [Line Items]  
Lease End Date 2030-02
For the year ended December 31, 2014 43
For the year ended December 31, 2015 86
For the year ended December 31, 2016 86
For the year ended December 31, 2017 89
For the year ended December 31, 2018 90
For the year ended December 31, 2019 90
Thereafter $ 972