Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Common Stock Additional Paid-in Capital [Member]	Common Stock Distributions in Excess of Earnings [Member]	Total Stockholders' Equity [Member]	Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2014	$ 2,723,936	$ 192,411	$ 863	$ 2,635,900	$ (162,964)	$ 2,666,210	$ 57,726
Beginning Balance, shares at Dec. 31, 2014			86,259,684
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,002				43,187	43,187	815
Issuance of common stock, shares			1,507,393
Issuance of common stock	113,097		$ 15	113,082		113,097
Issuance of share-based compensation awards	413			413		413
Noncash amortization of share-based compensation	4,302			4,302		4,302
Exercise of stock options, shares			237,000
Exercise of stock options	10,482		$ 2	10,480		10,482
Repurchase of common stock, stock options and restricted stock units, shares			(20,429)
Repurchase of common stock, stock options and restricted stock units	(1,821)			(1,821)		(1,821)
Settlement of restricted stock units for shares of common stock, shares			36,699
Settlement of restricted stock units for shares of common stock	0			0		0
Exchange of common units of the Operating Parternship, shares			11,030
Exchange of common units of the Operating Partnership	0			316		316	(316)
Adjustment for noncontrolling interest	0			(1,496)		(1,496)	1,496
Preferred dividends	(3,313)				(3,313)	(3,313)
Dividends declared per common share and common unit ($0.35 per share/unit)	(31,892)				(31,265)	(31,265)	(627)
Ending Balance, shares at Mar. 31, 2015			88,031,377
Ending Balance at Mar. 31, 2015	2,859,206	192,411	$ 880	2,761,176	(154,355)	2,800,112	59,094
Beginning Balance at Dec. 31, 2015	$ 3,234,586	192,411	$ 923	3,047,894	(70,262)	3,170,966	63,620
Beginning Balance, shares at Dec. 31, 2015	92,258,690		92,258,690
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 178,113				174,308	174,308	3,805
Issuance of share-based compensation awards	404			404		404
Noncash amortization of share-based compensation	5,911			5,911		5,911
Exercise of stock options, shares			6,000
Exercise of stock options	256		$ 0	256		256
Repurchase of common stock, stock options and restricted stock units, shares			(92,089)
Repurchase of common stock, stock options and restricted stock units	(5,619)		$ (1)	(5,618)		(5,619)
Settlement of restricted stock units for shares of common stock, shares			55,663
Settlement of restricted stock units for shares of common stock	(1)			(1)		(1)
Issuance of common units in connection with acquisition (Note 2)	48,033						48,033
Exchange of common units of the Operating Parternship, shares			1,200
Exchange of common units of the Operating Partnership	0			39		39	(39)
Adjustment for noncontrolling interest	0			18,109		18,109	(18,109)
Preferred dividends	(3,313)				(3,313)	(3,313)
Dividends declared per common share and common unit ($0.35 per share/unit)	$ (33,672)				(32,752)	(32,752)	(920)
Ending Balance, shares at Mar. 31, 2016	92,229,464		92,229,464
Ending Balance at Mar. 31, 2016	$ 3,424,698	$ 192,411	$ 922	$ 3,066,994	$ 67,981	$ 3,328,308	$ 96,390