Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net income	$ 237,952	$ 217,535	$ 208,764
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss during the period	32,755	208,015	(21,568)
Reclassification adjustment for net (gains) losses included in net income	(4,314)	(6,414)	(6)
Total securities available for sale	28,441	201,601	(21,574)
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss	(9,405)	(22,463)	(887)
Derivatives:
Change in the accumulated gain/loss on effective cash flow hedge derivatives	(783)	(2,321)	61,553
Reclassification adjustments for (gains) losses included in net income:
Interest rate swaps on variable-rate loans	(37,380)	(37,380)	(43,389)
Interest rate swap on junior subordinated deferrable interest debentures	4,224	4,386	4,367
Total derivatives	(33,939)	(35,315)	22,531
Other comprehensive income (loss), before tax	(14,903)	143,823	70
Deferred tax expense (benefit) related to other comprehensive income	(5,217)	50,339	25
Other comprehensive income (loss), net of tax	(9,686)	93,484	45
Comprehensive income	$ 228,266	$ 311,019	$ 208,809