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	$ 61,033	$ 51,928
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss during the period	1,882	8,290
Reclassification adjustment for net (gains) losses included in net income	491	(5)
Total securities available for sale	2,373	8,285
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss	1,229	783
Derivatives:
Change in the accumulated gain/loss on effective cash flow hedge derivatives	(427)	65
Reclassification adjustments for (gains) losses included in net income:
Interest rate swaps on variable-rate loans	(9,345)	(9,345)
Interest rate swap on junior subordinated deferrable interest debentures	1,033	1,086
Total derivatives	(8,739)	(8,194)
Other comprehensive income(loss), before tax	(5,137)	874
Deferred tax expense (benefit) related to other comprehensive income	(1,799)	306
Other comprehensive income (loss), net of tax	(3,338)	568
Comprehensive income	$ 57,695	$ 52,496