Accumulated Other Comprehensive Income Components of Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ (37,341)	$ 5,675
Other comprehensive income (loss) before reclassifications	16,266	1,208
Amounts reclassified from accumulated other comprehensive income (loss)	(814)	(1,246)
Ending Balance	(21,889)	5,637
Unrealized Gains on Investment Securities Not Other-Than-Temporarily Impaired [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(27,510)	26,361
Other comprehensive income (loss) before reclassifications	13,933	125
Amounts reclassified from accumulated other comprehensive income (loss)	0	(1,608)
Ending Balance	(13,577)	24,878
Unrealized Non-Credit Losses on Other-Than-Temporarily Impaired Debt Securities [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	1,652	613
Other comprehensive income (loss) before reclassifications	189	1,083
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Ending Balance	1,841	1,696
Unrealized Effective Portions of Losses on Forward-Starting Interest Rate Swaps [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2,682)	(2,818)
Amounts reclassified from accumulated other comprehensive income (loss)	34	34
Ending Balance	(2,648)	(2,784)
Unrecognized Pension and Postretirement Plan Items [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(8,801)	(18,481)
Other comprehensive income (loss) before reclassifications	2,144
Amounts reclassified from accumulated other comprehensive income (loss)	(848)	328
Ending Balance	$ (7,505)	$ (18,153)