Condensed Parent Company Financial Statements (Statements Of Income) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income
(Losses) gains on available-for-sale securities, net	$ 18,000	$ (153,000)	$ (336,000)	$ (33,000)	$ (3,328,000)	$ 75,000	$ 2,000	$ 251,000	$ (504,000)	$ (3,000,000)	$ 4,895,000
Expenses
Interest expense	18,996,000	19,006,000	17,370,000	17,320,000	18,274,000	19,386,000	20,822,000	21,600,000	72,692,000	80,082,000	107,505,000
Salaries and employee benefits									335,506,000	308,794,000	288,589,000
Income before taxes	61,802,000	65,258,000	63,031,000	56,340,000	57,822,000	58,082,000	56,250,000	52,286,000	246,431,000	224,440,000	180,132,000
Total income tax benefit	(23,669,000)	(25,034,000)	(24,490,000)	(21,840,000)	(22,534,000)	(22,519,000)	(21,943,000)	(20,234,000)	(95,033,000)	(87,230,000)	(68,936,000)
Net income	38,133,000	40,224,000	38,541,000	34,500,000	35,288,000	35,563,000	34,307,000	32,052,000	151,398,000	137,210,000	111,196,000
Reportable Legal Entities [Member] | Parent Company [Member]
Income
Dividends and other revenue from subsidiaries									98,296,000	114,241,000	47,295,000
(Losses) gains on available-for-sale securities, net									(33,000)	111,000	64,000
Other income									221,000	4,529,000	605,000
Total income									98,484,000	118,881,000	47,964,000
Expenses
Interest expense									12,553,000	13,424,000	16,840,000
Salaries and employee benefits									30,636,000	17,831,000	20,042,000
Other expenses									38,428,000	24,739,000	27,428,000
Total expenses									81,617,000	55,994,000	64,310,000
Income before taxes									16,867,000	62,887,000	(16,346,000)
Total income tax benefit									22,909,000	18,599,000	23,127,000
Income (loss) before equity in undistributed net loss of subsidiaries									39,776,000	81,486,000	6,781,000
Equity in undistributed net income of subsidiaries									111,622,000	55,724,000	104,415,000
Net income									$ 151,398,000	$ 137,210,000	$ 111,196,000