Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Series A Preferred Stock [Member]	Series C Preferred Stock [Member]	Preferred Stock [Member] Series A Preferred Stock [Member]	Preferred Stock [Member] Series C Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series A Preferred Stock [Member]	Additional Paid-in Capital [Member] Series C Preferred Stock [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings (Deficit) [Member]	Retained Earnings (Deficit) [Member] Series C Preferred Stock [Member]
Balance at Dec. 31, 2012	$ 3,569,431			$ 957,327	$ 0	$ 113,182	$ 2,868,965			$ (114,176)	$ 4,101	$ (259,968)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	159,383											159,383
Other comprehensive income (loss), net of income taxes	(45,359)										(45,359)
Cash dividends declared on common stock	(36,427)											(36,427)
Cash dividends paid		$ (33,741)	$ (2,730)					$ (33,741)	$ (2,730)
Accretion of discount on Series A Preferred Stock				10,543				$ (10,543)
Redemption of Series A Preferred Stock		$ (967,870)		(967,870)
Issuance of common stock, net of issuance costs	175,174		125,862		125,862	8,553	166,621
Settlement of prepaid common stock purchase contracts						17,550	(17,550)
Restricted share unit activity	(3,564)					374	(3,438)					(500)
Stock options exercised	1,044					62	982
Share-based compensation tax benefit (deficiency)	317						317
Share-based compensation expense	7,465						7,465
Balance at Dec. 31, 2013	2,948,985			0	125,862	139,721	2,976,348			(114,176)	(41,258)	(137,512)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	195,249											195,249
Other comprehensive income (loss), net of income taxes	28,653										28,653
Cash dividends declared on common stock	(42,805)											(42,805)
Cash dividends paid			(10,238)						(10,238)
Redemption of Series A Preferred Stock	(88,113)						(14,515)			(73,598)
Issuance of common stock, net of issuance costs			118		118
Restricted share unit activity	(692)					52	(706)					(38)
Stock options exercised	3,048					177	2,871
Share-based compensation tax benefit (deficiency)	(3,168)						(3,168)
Share-based compensation expense	10,233						10,233
Balance at Dec. 31, 2014	3,041,270			0	125,980	139,950	2,960,825			(187,774)	(12,605)	14,894
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	226,082											226,082
Other comprehensive income (loss), net of income taxes	(17,214)										(17,214)
Cash dividends declared on common stock	(55,354)											(55,354)
Cash dividends paid			$ (10,238)						$ 0				$ (10,238)
Redemption of Series A Preferred Stock	(199,221)						14,516			(213,737)
Restricted share unit activity	(4,984)					304	(4,877)					(411)
Stock options exercised	5,643					338	5,305
Share-based compensation tax benefit (deficiency)	1,656						1,656
Share-based compensation expense	12,556						12,556
Balance at Dec. 31, 2015	$ 3,000,196			$ 0	$ 125,980	$ 140,592	$ 2,989,981			$ (401,511)	$ (29,819)	$ 174,973