CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total stockholders' equity USD ($)	Preferred stock	Common stock	Preferred stock and paid in capital USD ($)	Common stock and paid in capital USD ($)	Distributions in excess of net income USD ($)	Noncontrolling interests USD ($)	Total USD ($)
Balance at Dec. 31, 2011	$ 2,254,854			$ 337,790	$ 2,563,048	$ (645,984)		$ 2,254,854
Balance (in shares) at Dec. 31, 2011		13,900,000	133,223,338
Increase (Decrease) in Stockholders' Equity
Net income	159,152					159,152		159,152
Distributions paid and payable	(278,133)					(278,133)		(278,133)
Shares issued in stock offerings, net of offering costs of $22,827, $55,359 and $13,773 for the year ended December 31, 2014, 2013 and 2012, respectively.	395,377			395,377				395,377
Shares issued in stock offerings, net of offering costs (in shares)		16,350,000
Shares issued pursuant to dividend reinvestment and stock purchase plan, net	2,051				2,051			2,051
Shares issued pursuant to dividend reinvestment and stock purchase plan, net (in shares)			55,598
Preferred shares redeemed	(127,500)			(123,804)		(3,696)		(127,500)
Preferred shares redeemed (in shares)		(5,100,000)
Share-based compensation	6,993				6,993			6,993
Share-based compensation (in shares)			173,475
Balance at Dec. 31, 2012	2,412,794			609,363	2,572,092	(768,661)		2,412,794
Balance (in shares) at Dec. 31, 2012		25,150,000	133,452,411
Increase (Decrease) in Stockholders' Equity
Net income	245,564					245,564	719	246,283
Distributions paid and payable	(468,697)					(468,697)	(1,371)	(470,068)
Shares issued in stock offerings, net of offering costs of $22,827, $55,359 and $13,773 for the year ended December 31, 2014, 2013 and 2012, respectively.	1,133,574				1,133,574			1,133,574
Shares issued in stock offerings, net of offering costs (in shares)			27,025,000
Shares issued in conjunction with acquisition of ARCT, net of our shares owned by ARCT	1,997,850				1,997,850			1,997,850
Shares issued in conjunction with acquisition of ARCT, net of our shares owned by ARCT (in shares)			45,364,435
Issuance of preferred and common units							36,563	36,563
Shares issued pursuant to dividend reinvestment and stock purchase plan, net	55,244				55,244			55,244
Shares issued pursuant to dividend reinvestment and stock purchase plan, net (in shares)			1,449,139
Share-based compensation	9,118				9,118			9,118
Share-based compensation (in shares)			194,088
Balance at Dec. 31, 2013	5,385,447			609,363	5,767,878	(991,794)	35,911	5,421,358
Balance (in shares) at Dec. 31, 2013		25,150,000	207,485,073
Increase (Decrease) in Stockholders' Equity
Net income	270,635					270,635	1,305	271,940
Distributions paid and payable	(519,790)					(519,790)	(1,839)	(521,629)
Shares issued in stock offerings, net of offering costs of $22,827, $55,359 and $13,773 for the year ended December 31, 2014, 2013 and 2012, respectively.	528,592				528,592			528,592
Shares issued in stock offerings, net of offering costs (in shares)			13,800,000
Redemption of common units	1,032				1,032		(1,032)
Redemption of common units (in shares)			35,000
Reallocation of equity	6,647				6,647		(6,647)
Shares issued pursuant to dividend reinvestment and stock purchase plan, net	157,285				157,285			157,285
Shares issued pursuant to dividend reinvestment and stock purchase plan, net (in shares)			3,527,166
Preferred shares redeemed	(220,000)			(213,985)		(6,015)		(220,000)
Preferred shares redeemed (in shares)		(8,800,000)
Share-based compensation	3,553				3,553			3,553
Share-based compensation (in shares)			33,953
Balance at Dec. 31, 2014	$ 5,613,401			$ 395,378	$ 6,464,987	$ (1,246,964)	$ 27,698	$ 5,641,099
Balance (in shares) at Dec. 31, 2014		16,350,000	224,881,192