Equity Investments (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended					1 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 SIR	Mar. 31, 2013 SIR	Mar. 31, 2014 AIC item	Apr. 30, 2014 AIC Subsequent Event
Income Statements:
Rental income	$ 172,040	$ 211,300	$ 45,063	$ 37,458
Tenant reimbursements and other income	45,220	51,312	7,965	6,402
Total revenues	217,260	262,612	53,028	43,860
Operating expenses	101,731	104,130	9,979	7,874
Depreciation and amortization			9,294	6,665
Acquisition related costs			238	533
General and administrative	24,848	16,663	5,176	2,719
Total expenses	173,472	183,991	24,687	17,791
Operating income	43,788	78,621	28,341	26,069
Interest expense	(37,935)	(51,896)	(3,358)	(3,473)
Gain on extinguishment of debt		(60,027)	243
Income from continuing operations before income tax expense and equity in earnings of investees	6,346	33,446	25,226	22,596
Income tax expense	(555)	(988)	(71)	(40)
Equity in earnings (loss) of an investee	10,934	4,262	(97)	76
Net income	20,448	35,624	25,058	22,632
Weighted average common shares outstanding			49,841,000	39,283,000
Per common share:
Net income per common share (in dollars per share)			$ 0.50	$ 0.58
Amount invested in equity investee					5,209
Combined carrying value of equity method investments					5,835
Number of other companies which are shareholders of related party					4
Equity method investments, ownership percentage			44.10%		12.50%
Equity investments, common shares sold						20,000
Equity investments, proceeds from sale						$ 5,776