Condensed Parent Company Financial Statements (Statements Of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income
Gains (losses) on available-for-sale securities, net	$ (79)	$ (98)	$ (24)	$ 524	$ 18	$ (153)	$ (336)	$ (33)	$ 323	$ (504)	$ (3,000)
Expenses
Interest expense	20,281	19,839	18,349	18,466	18,996	19,006	17,370	17,320	76,935	72,692	80,082
Salaries and employee benefits									382,080	335,506	308,794
(Loss) income before income taxes and equity in undistributed income of subsidiaries	56,408	62,197	70,126	63,035	61,802	65,258	63,031	56,340	251,765	246,431	224,440
Total income tax benefit	(20,896)	(23,842)	(26,295)	(23,983)	(23,669)	(25,034)	(24,490)	(21,840)	(95,016)	(95,033)	(87,230)
Net income	$ 35,512	$ 38,355	$ 43,831	$ 39,052	$ 38,133	$ 40,224	$ 38,541	$ 34,500	156,749	151,398	137,210
Reportable Legal Entities [Member] | Parent Company [Member]
Income
Dividends and other revenue from subsidiaries									47,639	98,296	114,241
Gains (losses) on available-for-sale securities, net									0	(33)	111
Other income									796	221	4,529
Total income									48,435	98,484	118,881
Expenses
Interest expense									16,669	12,553	13,424
Salaries and employee benefits									38,926	30,636	17,831
Other expenses									50,425	38,428	24,739
Total expenses									106,020	81,617	55,994
(Loss) income before income taxes and equity in undistributed income of subsidiaries									(57,585)	16,867	62,887
Total income tax benefit									30,504	22,909	18,599
(Loss) income before equity in undistributed net income of subsidiaries									(27,081)	39,776	81,486
Equity in undistributed net income of subsidiaries									183,830	111,622	55,724
Net income									$ 156,749	$ 151,398	$ 137,210