Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Consolidated Statements Of Comprehensive Income [Abstract]
Net income	$ 21,723	$ 16,433
Change in securities available-for-sale:
Unrealized holding gains for the period	6,240	8,523
Reclassification adjustment for securities gains realized in income	(619)	(1,499)
Other-than-temporary-impairment on available-for-sale securities associated with credit loss realized in income	96	299
Income tax effect	(2,316)	(2,682)
Unrealized gains on available-for-sale securities	3,401	4,641
Change in securities held-to-maturity:
Amortization of fair value for securities held-to-maturity previously recognized into accumulated other comprehensive income	(230)	(493)
Income tax effect	92	197
Changes from securities held-to-maturity	(138)	(296)
Cash flow hedges:
Net unrealized derivative gains (losses) on cash flow hedges	(240)	(318)
Reclassification adjustment on cash flow hedges	0	72
Income Tax Effect	96	99
Changes from cash flow hedges	(144)	(147)
Defined benefit pension plans:
Amortization of net loss recognized in income	1,007	903
Income tax effect	(403)	(362)
Changes from defined benefit pension plans	604	541
Other comprehensive income, net of tax	3,723	4,739
Comprehensive income	$ 25,446	$ 21,172