Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 237,866	$ 237,952	$ 217,535
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss during the period	(115,245)	33,412	208,015
Change in net unrealized gain on securities transferred to held-to-maturity	(35,682)	(657)	0
Reclassification adjustment for net (gains) losses included in net income	(1,176)	(4,314)	(6,414)
Total securities available for sale and transferred securities	(152,103)	28,441	201,601
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss	35,293	(9,405)	(22,463)
Derivatives:
Change in the accumulated gain/loss on effective cash flow hedge derivatives	(49)	(783)	(2,321)
Reclassification adjustments for (gains) losses included in net income:
Interest rate swaps on variable-rate loans	(37,380)	(37,380)	(37,380)
Interest rate swap on junior subordinated deferrable interest debentures	4,064	4,224	4,386
Total derivatives	(33,365)	(33,939)	(35,315)
Other comprehensive income (loss), before tax	(150,175)	(14,903)	143,823
Deferred tax expense (benefit) related to other comprehensive income	(52,561)	(5,217)	50,339
Other comprehensive income (loss), net of tax	(97,614)	(9,686)	93,484
Comprehensive income	$ 140,252	$ 228,266	$ 311,019