Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred stock	Common stock	Other paid-in capital	Retained earnings	Accumulated other comprehensive loss	Treasury stock
Balance (in shares) at Dec. 31, 2016		150,000
Balance (in shares) at Dec. 31, 2016			195,843,297
Treasury stock (in shares) at Dec. 31, 2016							(538,921)
Balance at Dec. 31, 2016	$ 2,316,244	$ 15,000	$ 195,843	$ 1,232,478	$ 912,282	$ (35,733)	$ (3,626)
Net income	165,891				165,891
Other comprehensive income	392					392
Dividends declared on preferred stocks	(171)				(171)
Dividends declared on common stock	(112,788)				(112,788)
Stock-based compensation	2,390			2,729	(339)
Repurchase of common stock							(64,384)
Repurchase of common stock	(1,684)						$ (1,684)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings				(2,441)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)							64,384
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings							$ 1,684
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(757)
Redemption of preferred stock (shares)		(150,000)
Redemption of preferred stock		$ (15,000)
Redemption of preferred stock	(600)				(600)
Redemption of preferred stock	$ (15,600)
Balance (in shares) at Sep. 30, 2017		0
Balance (in shares) at Sep. 30, 2017	195,843,297		195,843,297
Treasury stock (in shares) at Sep. 30, 2017							(538,921)
Balance at Sep. 30, 2017	$ 2,353,917	$ 0	$ 195,843	1,232,766	964,275	(35,341)	$ (3,626)
Balance at Jun. 30, 2017						(35,789)
Net income	87,351
Other comprehensive income	448					448
Redemption of preferred stock	$ 0
Balance (in shares) at Sep. 30, 2017		0
Balance (in shares) at Sep. 30, 2017	195,843,297		195,843,297
Treasury stock (in shares) at Sep. 30, 2017							(538,921)
Balance at Sep. 30, 2017	$ 2,353,917	$ 0	$ 195,843	1,232,766	964,275	(35,341)	$ (3,626)
Cumulative effect of adoption of ASU 2014-09 | Accounting Standards Update 2014-09	(970)				(970)
Adjusted balance at January 1, 2018	$ 2,428,073		$ 195,843	1,233,412	1,039,778	(37,334)	$ (3,626)
Balance (in shares) at Dec. 31, 2017	195,843,297		195,843,297
Treasury stock (in shares) at Dec. 31, 2017							(538,921)
Balance at Dec. 31, 2017	$ 2,429,043		$ 195,843	1,233,412	1,040,748	(37,334)	$ (3,626)
Net income	193,490				193,490
Other comprehensive income	1,674					1,674
Reclassification of certain prior period tax effects from accumulated other comprehensive loss | Adjustments for new accounting pronouncement	0				7,959	(7,959)
Dividends declared on common stock	(115,998)				(115,998)
Stock-based compensation	3,411			3,810	(399)
Repurchase of common stock							(182,424)
Repurchase of common stock	(5,020)						$ (5,020)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings				(7,350)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)							182,424
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings							$ 5,020
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(2,330)
Issuance of common stock (shares)			713,948
Issuance of common stock	17,993		$ 714	17,279
Redemption of preferred stock	0
Redemption of preferred stock	$ 0
Balance (in shares) at Sep. 30, 2018	196,557,245		196,557,245
Treasury stock (in shares) at Sep. 30, 2018							(538,921)
Balance at Sep. 30, 2018	$ 2,521,293		$ 196,557	1,247,151	1,124,830	(43,619)	$ (3,626)
Balance at Jun. 30, 2018						(44,135)
Net income	107,251
Other comprehensive income	516					516
Redemption of preferred stock	$ 0
Balance (in shares) at Sep. 30, 2018	196,557,245		196,557,245
Treasury stock (in shares) at Sep. 30, 2018							(538,921)
Balance at Sep. 30, 2018	$ 2,521,293		$ 196,557	$ 1,247,151	$ 1,124,830	$ (43,619)	$ (3,626)