Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 167,699	$ 134,348	$ 195,028
Unrealized gains and losses on securities:
Change in unrealized securities gains (losses) arising during period	(50,441)	9,566	3,108
Deferred tax benefit (expense)	19,833	(3,759)	(1,148)
Reclassification adjustment for losses (gains) included in income before income taxes	0	(2,322)	262
Deferred tax expense (benefit)	0	917	(159)
Total change in unrealized gains (losses) on securities, net of tax	(30,608)	4,402	2,063
Change in fair value of cash flow hedges:
Change in unrecognized loss on cash flow hedges	(103)	(2,779)	(8,329)
Deferred tax benefit	43	1,097	3,289
Reclassification adjustment for losses included in income before income taxes	3,281	3,095	7,107
Deferred tax benefit	(1,363)	(1,222)	(2,806)
Total change in unrecognized loss on cash flow hedges, net of tax	1,858	191	(739)
Change in pension obligation:
Change in pension obligation	123,557	(44,315)	(58,630)
Deferred tax benefit (expense)	(48,475)	17,354	22,959
Reclassification adjustment for losses included in income before income taxes	17,195	11,236	7,071
Deferred tax benefit	(6,689)	(4,400)	(2,769)
Total change in pension obligation, net of tax	85,588	(20,125)	(31,369)
Net current period other comprehensive income (loss)	56,838	(15,532)	(30,045)
Total comprehensive income	$ 224,537	$ 118,816	$ 164,983