Shareholders' Equity Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	$ (32,974)	$ (38,449)	$ (22,017)
Other comprehensive loss before reclassifications	(22,704)	10,008	(16,007)
Amounts reclassified from accumulated other comprehensive (loss) income	1,618	(4,533)	(425)
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	2,098
Reclassification of stranded tax effects	(7,101)
Ending Balance	(59,063)	(32,974)	(38,449)
Unrealized Gain (Losses) on Investment Securities Not Other-Than-Temporarily Impaired
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	(18,509)	(23,047)	(6,499)
Other comprehensive loss before reclassifications	(24,326)	10,432	(14,891)
Amounts reclassified from accumulated other comprehensive (loss) income	(30)	(5,894)	(1,657)
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	2,098
Reclassification of stranded tax effects	(3,887)
Ending Balance	(44,654)	(18,509)	(23,047)
Unrealized Non-Credit Gains (Losses) on Other-Than-Temporarily Impaired Debt Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	458	273	458
Other comprehensive loss before reclassifications	222	185	(185)
Amounts reclassified from accumulated other comprehensive (loss) income	0	0	0
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	0
Reclassification of stranded tax effects	0
Ending Balance	680	458	273
Unrealized Effective Portions of Losses on Forward-Starting Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	0	0	(15)
Other comprehensive loss before reclassifications	0	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	0	0	15
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	0
Reclassification of stranded tax effects	0
Ending Balance	0	0	0
Unrecognized Pension and Postretirement Plan Income (Cost)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	(14,923)	(15,675)	(15,961)
Other comprehensive loss before reclassifications	1,400	(609)	(931)
Amounts reclassified from accumulated other comprehensive (loss) income	1,648	1,361	1,217
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	0
Reclassification of stranded tax effects	(3,214)
Ending Balance	$ (15,089)	$ (14,923)	$ (15,675)