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	9 Months Ended
	Jul. 09, 2014	Sep. 30, 2015	Sep. 30, 2014	Jul. 09, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statements:
Rental income		$ 125,459	$ 174,216		$ 457,128	$ 518,663
Tenant reimbursements and other income		33,749	42,379		118,829	130,386
Total revenues		159,208	216,595		575,957	649,049
Operating expenses		73,571	99,392		261,128	293,824
General and administrative		16,249	47,450		43,718	96,395
Total expenses		130,342	204,055		478,866	576,839
Operating income		28,866	12,540		97,091	72,210
Interest expense		(25,111)	(35,245)		(82,926)	(111,079)
(Loss) gain on early extinguishment of debt		(3,887)	6,699		6,111	6,699
Income before income tax expense and equity in earnings of an investee		30,489	156,154		59,089	157,642
Income tax expense		(23)	(703)		(2,377)	(2,166)
Equity in earnings of investees		0	1,072		0	24,460
Net income		$ 30,466	$ 156,740		$ 56,712	$ 182,573
Weighted average common shares outstanding (in shares)		128,739	128,880		129,386	123,736
Net income per common share (in dollars per share)		$ 0.18	$ 1.16		$ 0.28	$ 1.14
SIR
Income Statements:
Rental income	$ 4,698			$ 98,226
Tenant reimbursements and other income	923			16,980
Total revenues	5,621			115,206
Operating expenses	1,018			20,982
Depreciation and amortization	1,043			20,832
Acquisition related costs	0			374
General and administrative	357			7,731
Total expenses	2,418			49,919
Operating income	3,203			65,287
Interest expense	(295)			(7,287)
(Loss) gain on early extinguishment of debt	0			243
Income before income tax expense and equity in earnings of an investee	2,908			58,243
Income tax expense	0			(90)
Equity in earnings of investees	11			32
Net income	$ 2,919			$ 58,185
Weighted average common shares outstanding (in shares)	59,889			52,394
Net income per common share (in dollars per share)	$ 0.05			$ 1.11