Derivative Financial Instruments Notional Amounts and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 331,269	$ 144,371
Derivative Liability, Fair Value, Gross Liability	(165,210)	(76,067)
Interest Rate Locks with Customers
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	382,903	132,260
Derivative Liability, Notional Amount	3,154	9,783
Derivative Asset, Fair Value, Gross Asset	8,034	1,123
Derivative Liability, Fair Value, Gross Liability	(35)	(53)
Forward Commitments
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	0	75,000
Derivative Liability, Notional Amount	292,262	180,000
Derivative Asset, Fair Value, Gross Asset	0	63
Derivative Liability, Fair Value, Gross Liability	(2,263)	(371)
Interest Rate Swaps with Customers
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	3,834,062	2,903,489
Derivative Liability, Notional Amount	45,640	376,705
Derivative Asset, Fair Value, Gross Asset	330,951	143,484
Derivative Liability, Fair Value, Gross Liability	(2)	(695)
Interest Rate Swaps with Dealer Counterparties
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	45,640	376,705
Derivative Liability, Notional Amount	3,834,062	2,903,489
Derivative Asset, Fair Value, Gross Asset	2	695
Derivative Liability, Fair Value, Gross Liability	(165,205)	(75,327)
Foreign Exchange Contracts with Customers
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	1,121	3,373
Derivative Liability, Notional Amount	5,963	7,283
Derivative Asset, Fair Value, Gross Asset	5	38
Derivative Liability, Fair Value, Gross Liability	(275)	(154)
Foreign Exchange Contracts with Correspondent Banks
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	6,372	9,028
Derivative Liability, Notional Amount	1,422	4,976
Derivative Asset, Fair Value, Gross Asset	318	192
Derivative Liability, Fair Value, Gross Liability	$ (5)	$ (45)

Nominal or face amount used to calculate payments on the derivative asset.

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