Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common stock	Warrant	Capital Surplus	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock
Beginning Balance at Dec. 31, 2012	$ 1,645,202	$ 0	$ 127,937	$ 0	$ 475,979	$ (16,205)	$ 1,195,850	$ (138,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	183,684	0	0	0	0	0	183,684	0
Other comprehensive income	(50,671)	0	0	0	0	(50,671)	0	0
Comprehensive income	133,013	0	0	0	0	(50,671)	183,684	0
Cash dividends - Preferred Stock	(5,337)	0	0	0	0	0	(5,337)	0
Cash dividends - common stock	(96,222)	0	0	0	0	0	(96,222)	0
Common stock issued in connection with Citizens acquisition (55,468,283 shares)	925,272				925,272
Nonvested (restricted) shares granted	(6,813)		0	0	(19,790)	0		12,977
Restricted stock activity	(2,708)	0	0	0	1,261	0	0	(3,969)
Deferred compensation trust	0	0	0	0	(434)	0	0	434
Issuance Non-Cumulative Perpetual Preferred Stock, Series A	96,550	100,000			(3,450)
Issuance of a Common Stock warrant to the U.S. Treasury for Citizens TARP warrant	(3,000)			(3,000)
Share-based compensation	10,937	0	0	0	10,937	0	0	0
Repurchase of common stock warrant	0
Ending Balance at Dec. 31, 2013	2,702,894	100,000	127,937	3,000	1,390,643	(66,876)	1,277,975	(129,785)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	237,951	0	0	0	0	0	237,951	0
Other comprehensive income	(5,016)	0	0	0	0	(5,016)	0	0
Comprehensive income	232,935	0	0	0	0	(5,016)	237,951	0
Cash dividends - Preferred Stock	(5,876)	0	0	0	0	0	(5,876)	0
Cash dividends - common stock	(105,333)	0	0	0	0	0	(105,333)	0
Nonvested (restricted) shares granted	99			0	(13,469)			13,568
Restricted stock activity	(4,360)	0	0	0	1,219	0	0	(5,579)
Deferred compensation trust	0	0	0	0	(775)	0	0	775
Issuance of a Common Stock warrant to the U.S. Treasury for Citizens TARP warrant	0
Share-based compensation	13,922	0	0	0	13,922	0	0	0
Repurchase of common stock warrant	0
Ending Balance at Dec. 31, 2014	2,834,281	100,000	127,937	3,000	1,393,090	(71,892)	1,404,717	(122,571)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	229,484	0	0	0	0	0	229,484	0
Other comprehensive income	(7,382)	0	0	0	0	(7,382)	0	0
Comprehensive income	222,102	0	0	0	0	(7,382)	229,484	0
Cash dividends - Preferred Stock	(5,876)	0	0	0	0	0	(5,876)	0
Cash dividends - common stock	(108,887)	0	0	0	0	0	(108,887)	0
Nonvested (restricted) shares granted	0			0	(14,798)		0	14,798
Restricted stock activity	(4,395)	0	0	0	1,917	0	0	(6,312)
Deferred compensation trust	0	0	0	0	(598)	0	0	598
Issuance of a Common Stock warrant to the U.S. Treasury for Citizens TARP warrant	0			(3,000)
Share-based compensation	15,020	0	0	0	15,020	0	0	0
Adjustments to Additional Paid in Capital, Other	9,200				(9,150)
Repurchase of common stock warrant	(12,150)
Ending Balance at Dec. 31, 2015	$ 2,940,095	$ 100,000	$ 127,937	$ 0	$ 1,386,677	$ (79,274)	$ 1,519,438	$ (114,683)