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	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), before Tax	$ (78,096)	$ (76,280)	$ (78,096)	$ (76,280)
Net losses/(gains) realized on sale of securities reclassified to noninterest income, before Tax	41	14	962	150
Net losses/(gains) realized on sale of securities reclassified to noninterest income, Tax	14	5	336	53
Net losses/(gains) realized on sale of securities reclassified to noninterest income, Net of Tax	(27)	(9)	(626)	(97)
Accumulated other comprehensive loss	(50,766)	(49,583)	(50,766)	(49,583)		$ (71,892)
accumulated other comprehensive income, tax	(27,330)	(26,697)	(27,330)	(26,697)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	(97,424)	(53,800)	(97,424)	(53,800)	$ (98,972)	(102,068)	$ (55,084)	$ (57,812)
Changes in unrealized securities' holding gains/(losses) that result from securities being transferred from available-for-sale to held-to-maturity, Tax	(442)	(197)	(821)	(543)
Accumulated Net Unrealized Investment Gain (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), before Tax	19,328	(22,480)	19,328	(22,480)	(5,056)	(8,531)	(5,696)	(45,072)
Accumulated other comprehensive loss	12,562	(14,612)	12,562	(14,612)	(3,287)	(5,546)	(3,702)	(29,297)
accumulated other comprehensive income, tax	$ 6,766	$ (7,868)	$ 6,766	$ (7,868)	$ (1,769)	$ (2,985)	$ (1,994)	$ (15,775)