Equity Investments - Summary of Income Statement Information of Equity Method Investee (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended			6 Months Ended
	Mar. 31, 2013	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 09, 2014
Equity Investments
Rental income										$ 691,699	$ 763,262	$ 774,600
Tenant reimbursements and other income										170,158	189,767	186,487
Total revenues		212,808	216,595	215,194	217,260	214,028	214,201	262,188	262,612	861,857	953,029	961,087
Operating expenses										387,982	410,045	397,673
General and administrative										113,155	80,504	49,312
Total expenses										913,741	849,522	682,917
Operating (loss) income										(51,884)	103,507	278,170
Interest and other income										1,561	1,229	1,410
Interest expense										(143,230)	(173,011)	(202,055)
Gain (loss) on early extinguishment of debt	(60,000)									4,909	(60,052)	(287)
(Loss) income from continuing operations before income tax expense and equity in earnings of investees										(63)	(62,034)	84,484
Income tax (expense) benefit										(3,191)	(2,634)	(3,207)
Equity in earnings of an investee										24,460	25,754	11,420
Income (loss) from continuing operations										21,206	(38,914)	92,697
Net income (loss)										24,012	(156,967)	(79,845)
GOV
Equity Investments
Rental income												203,700
Operating expenses												75,326
Depreciation and amortization												49,070
Acquisition related costs												1,614
General and administrative												11,924
Total expenses												137,934
Operating (loss) income												65,766
Interest and other income												29
Interest expense												(16,892)
(Loss) income from continuing operations before income tax expense and equity in earnings of investees												48,903
Income tax (expense) benefit												(159)
Equity in earnings of an investee												316
Income (loss) from continuing operations												49,060
Income from discontinued operations												900
Net income (loss)												49,960
Weighted average common shares outstanding (in shares)												48,617
Income from continuing operations (in dollars per share)												$ 1.01
Income from discontinued operations (in dollars per share)												$ 0.02
Net income per common share (in dollars per share)												$ 1.03
SIR
Equity Investments
Rental income											159,011	105,559	98,226
Tenant reimbursements and other income											29,312	17,231	16,980
Total revenues											188,323	122,790	115,206
Operating expenses											36,382	23,796	20,982
Depreciation and amortization											31,091	14,860	20,832
Acquisition related costs											2,002	2,470	374
General and administrative											12,423	8,203	7,731
Total expenses											81,898	49,329	49,919
Operating (loss) income											106,425	73,461	65,287
Interest expense											(13,763)	(7,565)	(7,287)
Gain (loss) on early extinguishment of debt											0	0	243
(Loss) income from continuing operations before income tax expense and equity in earnings of investees											92,662	65,896	58,243
Income tax (expense) benefit											96	(290)	(90)
Equity in earnings of an investee											334	269	32
Net income (loss)											$ 93,092	$ 65,875	$ 58,185
Weighted average common shares outstanding (in shares)											44,565	27,122	52,394
Net income per common share (in dollars per share)											$ 2.09	$ 2.43	$ 1.11