Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Equity	Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2013	$ 2,891,290	$ 61,862	$ 1,750	$ 1,617,990	$ 1,392,508	$ (24,244)	$ (158,576)
Common stock shares outstanding, beginning balance (in shares) at Dec. 31, 2013			175,013
Preferred stock shares outstanding, beginning balance (in shares) at Dec. 31, 2013		64
Comprehensive income:
Net income	190,509	$ 0	$ 0	0	190,509	0	0
Other comprehensive income	19,394	$ 0	$ 0	0	0	19,394	0
Comprehensive income	209,903
Common stock issued:
Stock-based compensation plans, net (in shares)		0	0
Stock-based compensation plans, net	13,228	$ 0	$ 0	2,553	(21,171)	0	31,846
Purchase of common stock returned to authorized but unissued (in shares)		0	(8,469)
Purchase of common stock returned to authorized but unissued	(150,498)	$ 0	$ (85)	(150,413)	0	0	0
Purchase of treasury stock	(112,312)	0	0	0	0	0	(112,312)
Cash dividends:
Common stock dividends	(58,710)	0	0	0	(58,710)	0	0
Preferred stock dividends	(5,002)	$ 0	$ 0	0	(5,002)	0	0
Purchase of preferred stock (in shares)		(2)	0
Purchase of preferred stock	(2,451)	$ (2,135)	$ 0	0	(316)	0	0
Stock-based compensation expense, net	16,091	0	0	16,091	0	0	0
Tax impact of stock-based compensation	(1,288)	0	0	(1,288)	0	0	0
Ending balance at Dec. 31, 2014	2,800,251	$ 59,727	$ 1,665	1,484,933	1,497,818	(4,850)	(239,042)
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2014			166,544
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2014		62
Comprehensive income:
Net income	188,301	$ 0	$ 0	0	188,301	0	0
Other comprehensive income	(27,766)	$ 0	$ 0	0	0	(27,766)	0
Comprehensive income	160,535
Common stock issued:
Stock-based compensation plans, net (in shares)		0	0
Stock-based compensation plans, net	20,054	$ 0	$ 0	3,316	(22,538)	0	39,276
Acquisition of Ahmann & Martin Co. (in shares)		0	2,621
Acquisition of Ahmann & Martin Co.	43,530	$ 0	$ 26	43,504	0	0	0
Purchase of common stock returned to authorized but unissued (in shares)		0	(4,965)
Purchase of common stock returned to authorized but unissued	(93,000)	$ 0	$ (49)	(92,951)	0	0	0
Purchase of treasury stock	(5,154)	0	0	0	0	0	(5,154)
Cash dividends:
Common stock dividends	(62,400)	0	0	0	(62,400)	0	0
Preferred stock dividends	(7,155)	$ 0	$ 0	0	(7,155)	0	0
Issuance of preferred stock (in shares)		65	0
Issuance of preferred stock	62,966	$ 62,966	$ 0	0	0	0	0
Other (In Shares)		0	0
Purchase of preferred stock (in shares)		(2)	0
Purchase of preferred stock	(1,335)	$ (1,209)	$ 0	0	(126)	0	0
Stockholders' Equity, Other	(766)	(105)	0	0	(661)	0	0
Stock-based compensation expense, net	18,202	0	0	18,202	0	0	0
Tax impact of stock-based compensation	1,518	0	0	1,518	0	0	0
Ending balance at Dec. 31, 2015	2,937,246	$ 121,379	$ 1,642	1,458,522	1,593,239	(32,616)	(204,920)
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2015			164,200
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2015		125
Comprehensive income:
Net income	200,274	$ 0	$ 0	0	200,274	0	0
Other comprehensive income	(22,063)	$ 0	$ 0	0	0	(22,063)	0
Comprehensive income	178,211
Common stock issued:
Stock-based compensation plans, net (in shares)		0	0
Stock-based compensation plans, net	21,748	$ 0	$ 0	1,940	(19,356)	0	39,164
Purchase of common stock returned to authorized but unissued (in shares)		0	(1,170)
Purchase of common stock returned to authorized but unissued	(20,007)	$ 0	$ (12)	(19,995)	0	0	0
Purchase of treasury stock	(5,074)	0	0	0	0	0	(5,074)
Cash dividends:
Common stock dividends	(67,855)	0	0	0	(67,855)	0	0
Preferred stock dividends	(8,903)	$ 0	$ 0	0	(8,903)	0	0
Issuance of preferred stock (in shares)		100	0
Issuance of preferred stock	97,066	$ 97,066	$ 0	0	0	0	0
Redemption of preferred stock	(58,903)	$ (57,338)	$ 0	0	(1,565)	0	0
Stock Redeemed or Called During Period, Shares		(60)	0
Purchase of preferred stock (in shares)		0	0
Purchase of preferred stock	(1,248)	$ (1,178)	$ 0	0	(70)	0	0
Stock-based compensation expense, net	21,971	0	0	21,971	0	0	0
Tax impact of stock-based compensation	(2,940)	0	0	(2,940)	0	0	0
Ending balance at Dec. 31, 2016	$ 3,091,312	$ 159,929	$ 1,630	$ 1,459,498	$ 1,695,764	$ (54,679)	$ (170,830)
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2016			163,030
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2016		165