Equity Investments - Summary of Unaudited Income Statement Information of Equity Method Investee (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jul. 09, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statements:
Rental income										$ 409,071	$ 570,382	$ 691,699
Tenant reimbursements and other income										91,609	144,509	170,158
Total revenues	$ 103,546	$ 114,632	$ 145,367	$ 137,135	$ 138,934	$ 159,208	$ 203,694	$ 213,055		500,680	714,891	861,857
Operating expenses										200,706	324,948	387,982
General and administrative										50,256	57,457	113,155
Total expenses										441,244	593,568	913,741
Operating income (loss)										59,436	121,323	(51,884)
Interest expense										(84,329)	(107,316)	(143,230)
(Loss) gain on early extinguishment of debt										(2,680)	6,661	4,909
Income (loss) from continuing operations before income taxes and equity in earnings of investees										233,639	102,221	(63)
Income tax expense										(745)	(2,364)	(3,191)
Equity in earnings of investees										0	0	24,460
Net income										$ 232,894	$ 99,857	$ 24,012
Weighted average common shares outstanding (in shares)										125,474	128,621	125,163
Net income per common share (in dollars per share)	$ 0.08	$ 0.67	$ 0.57	$ 0.31	$ 0.29	$ 0.18	$ 0.04	$ 0.05		$ 1.64	$ 0.56	$ (0.19)
SIR
Income Statements:
Rental income									$ 98,226
Tenant reimbursements and other income									16,980
Total revenues									115,206
Operating expenses									20,982
Depreciation and amortization									20,832
Acquisition related costs									374
General and administrative									7,731
Total expenses									49,919
Operating income (loss)									65,287
Interest expense									(7,287)
(Loss) gain on early extinguishment of debt									243
Income (loss) from continuing operations before income taxes and equity in earnings of investees									58,243
Income tax expense									(90)
Equity in earnings of investees									32
Net income									$ 58,185
Weighted average common shares outstanding (in shares)									52,394
Net income per common share (in dollars per share)									$ 1.11