Quarterly Results Of Operations (Schedule Of Adjustments Of Operations) (Details) (USD $)	3 Months Ended								12 Months Ended						9 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009		Sep. 30, 2011 As Previously Reported [Member]	Sep. 30, 2011 Adjustment [Member]	Sep. 30, 2011 As Adjusted [Member]
Interest income	$ 111,799,000	$ 111,966,000	$ 97,127,000	$ 99,434,000	$ 97,716,000	$ 99,818,000	$ 101,217,000	$ 97,620,000	$ 420,327,000		$ 396,371,000		$ 270,387,000		$ 113,430,000	$ (1,464,000)	$ 111,966,000
Net interest income	92,573,000	90,971,000	75,965,000	78,748,000	72,349,000	69,933,000	70,139,000	69,206,000	338,258,000		281,627,000		172,785,000		92,435,000	(1,464,000)	90,971,000
Net interest income after provision for loan losses	88,295,000	84,844,000	65,975,000	73,277,000	61,125,000	64,805,000	57,240,000	56,005,000	312,391,000		239,176,000		127,415,000		86,308,000	(1,464,000)	84,844,000
Income before income taxes	24,024,000	22,398,000	4,257,000	19,840,000	18,075,000	21,215,000	12,169,000	17,358,000	70,519,000		68,817,000		248,692,000		23,862,000	(1,464,000)	22,398,000
Income tax expense	6,667,000	6,051,000	(929,000)	5,193,000	5,033,000	7,275,000	3,329,000	4,354,000	16,981,000		19,991,000		90,338,000		6,563,000	(512,000)	6,051,000
Net Income	17,357,000	16,347,000	5,186,000	14,647,000	13,042,000	13,940,000	8,840,000	13,004,000	53,538,000		48,826,000		158,354,000		17,299,000	(952,000)	16,347,000
Income Available to Common Shareholders - Basic	17,357,000	16,347,000	5,186,000	14,647,000	13,042,000	13,940,000	8,840,000	13,004,000	53,538,000		48,826,000		155,004,000		17,299,000	(952,000)	16,347,000
Income Available to Common Shareholders - Diluted	$ 17,050,000	$ 16,057,000	$ 5,099,000	$ 14,356,000	$ 12,781,000	$ 13,652,000	$ 8,651,000	$ 12,752,000	$ 52,571,000		$ 47,855,000		$ 151,094,000		$ 16,992,000	$ (935,000)	$ 16,057,000
Earnings per common share - Basic	$ 0.59	$ 0.55	$ 0.19	$ 0.54	$ 0.49	$ 0.52	$ 0.33	$ 0.60	$ 1.88	[1]	$ 1.90	[1]	$ 8.49	[1]	$ 0.58	$ 0.03	$ 0.55
Earnings per common share - Diluted	$ 0.59	$ 0.54	$ 0.18	$ 0.54	$ 0.48	$ 0.52	$ 0.33	$ 0.59	$ 1.87		$ 1.88		$ 8.41		$ 0.58	$ 0.04	$ 0.54

[1] Total earnings available to common shareholders include distributed earnings of $38,681,000, or $1.38 per weighted average share, and undistributed earnings of $13,869,000, or $0.50 per weighted average share for the year ended December 31, 2011. Total earnings available to common shareholders include distributed earnings of $35,772,000, or $1.42 per weighted average share, and undistributed earnings of $12,073,000, or $0.48 per weighted average share for the year ended December 31, 2010. Total earnings available to common shareholders include distributed earnings of $24,491,000, or $1.38 per weighted average share, and undistributed earnings of $126,296,000, or $7.11 per weighted average share for the year ended December 31, 2009.