Derivative Financial Instruments Fair Value Gains and Losses on Derivative Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income
Derivatives, Fair Value [Line Items]
Net fair value gains on derivative financial instruments	$ 8,767	$ 2,787	$ 1,157
Centrally Cleared Interest Rate Swap With Counterparty
Derivatives, Fair Value [Line Items]
Derivative Asset, Collateral, Obligation to Return Cash, Offset	14,300	4,600
Derivatives variation margin	9,700	4,600
Interest rate locks with customers \| Mortgage Banking Income
Derivatives, Fair Value [Line Items]
Gain (loss) on interest rate derivative instruments	136	364	(639)
Forward Commitments \| Mortgage Banking Income
Derivatives, Fair Value [Line Items]
Gain (loss) on interest rate derivative instruments	(884)	(2,290)	1,930
Interest Rate Swaps with Customers \| Other Income
Derivatives, Fair Value [Line Items]
Gain (loss) on interest rate derivative instruments	(3,038)	(1,872)	(25,461)
Interest Rate Swaps with Dealer Counterparties \| Other Income
Derivatives, Fair Value [Line Items]
Gain (loss) on interest rate derivative instruments	12,628	6,576	25,461
Foreign Exchange Contracts with Correspondent Banks \| Other Income
Derivatives, Fair Value [Line Items]
Gain (loss) on foreign currency derivatives	228	135	(487)
Foreign exchange contracts with customers \| Other Income
Derivatives, Fair Value [Line Items]
Gain (loss) on foreign currency derivatives	$ (303)	$ (126)	$ 353

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

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Aggregate impact of foreign currency derivatives on earnings for the period. Includes impact of foreign currency cash flow hedge ineffectiveness and the ineffectiveness of fair value hedging derivatives and full change in fair value of the foreign currency derivatives not designated as hedging instruments.

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