Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			$ (62,758)
Debt Securities, Available-for-sale, Realized Loss			2,015	$ 0
Personnel expense	$ 123,980	$ 107,066	241,665	213,848
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)	335	1,548	632	2,575
Total other comprehensive income (loss)	(12,215)	2,874	(57,130)	1,209
Ending Balance	(119,888)		(119,888)
Investment Securities Available For Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(78,453)	(22,023)	(38,453)	(20,079)
Other comprehensive income (loss) before reclassifications	(18,919)	5,744	(60,754)	3,632
Debt Securities, Available-for-sale, Realized Loss	2,015
Personnel expense	0	0	0	0
Other Expenses	0	0	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)	(335)	(1,548)	(632)	(2,575)
Income tax (expense) benefit	4,705	(1,601)	15,340	(406)
Total other comprehensive income (loss)	(12,533)	2,595	(52,533)	651
Ending Balance	(90,986)	(19,428)	(90,986)	(19,428)
Defined Benefit Pension and Post Retirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(29,220)	(34,321)	(24,305)	(34,600)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Debt Securities, Available-for-sale, Realized Loss	0
Personnel expense	(38)	(37)	(76)	(75)
Other Expenses	465	487	929	975
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	0	0
Income tax (expense) benefit	(109)	(171)	(216)	(342)
Total other comprehensive income (loss)	318	279	(4,597)	558
Ending Balance	(28,902)	(34,042)	(28,902)	(34,042)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(107,673)	(56,344)	(62,758)	(54,679)
Other comprehensive income (loss) before reclassifications	(18,919)	5,744	(60,754)	3,632
Debt Securities, Available-for-sale, Realized Loss	2,015
Personnel expense	(38)	(37)	(76)	(75)
Other Expenses	465	487	929	975
Change in Equity Securities(2016-01)			(84)
Reporting Comprehensive Income(2018-02)	(13,654)		(13,654)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(335)	(1,548)	(632)	(2,575)
Income tax (expense) benefit	4,596	(1,772)	15,124	(748)
Total other comprehensive income (loss)	12,215	2,874	(57,130)	1,209
Ending Balance	$ (119,888)	$ (53,470)	$ (119,888)	$ (53,470)

Accumulated Other Comprehensive Income (Loss) [Roll Forward]

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Amortization of Net Unrealized Gain on Available-for-Sale Securities Transfered to Held-to-maturity Securities

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Change in Equity Securities(2016-01)

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Reporting Comprehensive Income(2018-02)

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of expense for salary, wage, profit sharing; incentive and equity-based compensation; and other employee benefit.

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Amount before tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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