Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Series C Preferred Stock	Series D Preferred Stock	Preferred Stock Series C Preferred Stock	Preferred Stock Series D Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Series C Preferred Stock	Retained Earnings Series D Preferred Stock
Beginning balance at Dec. 31, 2015	$ 3,000,196			$ 125,980	$ 0	$ 140,592	$ 2,989,981	$ (401,511)	$ (29,819)	$ 174,973
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	246,784									246,784
Other comprehensive (loss) income, net of income taxes	(25,840)								(25,840)
Cash dividends declared on common stock	(59,425)									(59,425)
Cash dividends paid on Preferred Stock		$ (10,238)									$ (10,238)
Repurchases of common stock	(263,084)					(262,900)		(263,084)
Issuance of common stock for acquisition	26,592					821	25,771
Restricted share unit vesting and taxes paid related to net share settlement	(5,041)					316	(5,030)			(327)
Stock options exercised	5,155					297	4,858
Share-based compensation net tax deficiency	(790)						(790)
Share-based compensation expense	13,615						13,615
Ending balance at Dec. 31, 2016	2,927,924			125,980	0	142,026	3,028,405	(664,595)	(55,659)	351,767
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption	0
Net income	275,474									275,474
Other comprehensive (loss) income, net of income taxes	905								905
Cash dividends declared on common stock	(72,506)									(72,506)
Cash dividends paid on Preferred Stock		(10,238)									(10,238)
Repurchases of common stock	(175,079)					(175,000)		(175,079)
Issuance of common stock for acquisition	5,460					118	5,342
Restricted share unit vesting and taxes paid related to net share settlement	(7,993)					336	(8,039)			(290)
Stock options exercised	3,440					198	3,242
Share-based compensation net tax deficiency	5,000
Share-based compensation expense	14,179						14,179
Ending balance at Dec. 31, 2017	2,961,566			125,980	0	142,678	3,043,129	(839,674)	(54,754)	544,207
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption	0
Adoption | Cumulative-effect adjustment from adoption of ASU 2014-09	(685)									(685)
Adoption | Reclassification from adoption of ASU 2018-02	0								(7,588)	7,588
Adoption | Cumulative-effect adjustment from adoption of ASU 2016-01	0								117	(117)
Net income	428,476									428,476
Other comprehensive (loss) income, net of income taxes	(32,195)								(32,195)
Cash dividends declared on common stock	(117,355)									(117,355)
Cash dividends paid on Preferred Stock		(7,678)	$ (6,300)								(7,678)	$ (6,300)
Repurchases of common stock	(175,072)	$ (130,000)		(125,980)		(175,000)		(175,072)			$ (4,020)
Issuance of Series D Preferred Stock, net of issuance costs	195,140				195,140
Issuance of common stock for acquisition	7,427					199	7,228
Restricted share unit vesting and taxes paid related to net share settlement	(8,504)					297	(8,452)			(349)
Stock options exercised	2,139					126	2,013
Share-based compensation net tax deficiency	3,300
Share-based compensation expense	16,643						16,643
Ending balance at Dec. 31, 2018	3,133,602			$ 0	$ 195,140	$ 143,300	$ 3,060,561	$ (1,014,746)	$ (94,420)	$ 843,767
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption	$ (685)