Changes and Reclassifications Out of Accumulated Other Comprehensive Income Tax Effect of Changes and Reclassifications Out of Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), before Tax	$ (76,280)	$ (128,634)	$ (76,280)	$ (128,634)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(14)	1	(150)	(2,802)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	(5)	0	(53)	(981)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	9	(1)	97	1,821
Accumulated other comprehensive loss	(49,583)	(83,613)	(49,583)	(83,613)		(66,876)
accumulated other comprehensive income, tax	(26,697)	(45,021)	(26,697)	(45,021)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	(53,800)	(110,188)	(53,800)	(110,188)	(55,084)	(57,812)	(110,188)	(110,188)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	(197)	(187)	(543)	(579)
Accumulated Net Unrealized Investment Gain (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), before Tax	(22,480)	(18,446)	(22,480)	(18,446)	(5,696)	(45,072)	(420)	85,259
Accumulated other comprehensive loss	(14,612)	(11,990)	(14,612)	(11,990)	(3,702)	(29,297)	(274)	55,418
accumulated other comprehensive income, tax	$ (7,868)	$ (6,456)	$ (7,868)	$ (6,456)	$ (1,994)	$ (15,775)	$ (146)	$ 29,841