Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (62,758)
Personnel expense	117,685	$ 106,782
Change in Equity Securities(2016-01)	84
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(297)	(1,027)
Total other comprehensive income (loss)	44,915	1,665
Ending Balance	(107,673)
Investment Securities Available For Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(38,453)	(20,079)
Other comprehensive income (loss) before reclassifications	41,834	(2,112)
Investment securities gain, net		0
Personnel expense	0	0
Other Expenses	0	0
Change in Equity Securities(2016-01)	(84)
Reporting Comprehensive Income(2018-02)	(8,419)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(297)	1,027
Income tax (expense) benefit	10,635	(1,195)
Total other comprehensive income (loss)	(40,000)	1,944
Ending Balance	(78,453)	(22,023)
Defined Benefit Pension and Post Retirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(24,305)	(34,600)
Other comprehensive income (loss) before reclassifications	0	0
Investment securities gain, net		0
Personnel expense	(38)	38
Other Expenses	465	(488)
Change in Equity Securities(2016-01)	0
Reporting Comprehensive Income(2018-02)	(5,235)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	0	0
Income tax (expense) benefit	(107)	171
Total other comprehensive income (loss)	(4,915)	(279)
Ending Balance	(29,220)	(34,321)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(62,758)	(54,679)
Other comprehensive income (loss) before reclassifications	41,834	(2,112)
Investment securities gain, net		0
Personnel expense	(38)	38
Other Expenses	465	(488)
Change in Equity Securities(2016-01)	(84)
Reporting Comprehensive Income(2018-02)	(13,654)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(297)	1,027
Income tax (expense) benefit	10,528	(1,024)
Total other comprehensive income (loss)	(44,915)	(1,665)
Ending Balance	$ (107,673)	$ (56,344)