Derivative Financial Instruments Notional Amounts and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative asset, fair value	$ 390,843	$ 144,371
Derivative liability, gross liability	(188,595)	(76,067)
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	463,202	132,260
Derivative liability, notional amount	6,003	9,783
Derivative asset, fair value	10,614	1,123
Derivative liability, gross liability	(51)	(53)
Forward Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	0	75,000
Derivative liability, notional amount	395,515	180,000
Derivative asset, fair value	0	63
Derivative liability, gross liability	(2,057)	(371)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	3,587,221	2,903,489
Derivative liability, notional amount	12,288	376,705
Derivative asset, fair value	390,701	143,484
Derivative liability, gross liability	(4)	(695)
Interest Rate Swap With Counterparty [Member]
Derivative [Line Items]
Derivative asset, notional amount	12,288	376,705
Derivative liability, notional amount	3,587,221	2,903,489
Derivative asset, fair value	4	695
Derivative liability, gross liability	(188,515)	(75,327)
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	7,174	3,373
Derivative liability, notional amount	5,248	7,283
Derivative asset, fair value	79	38
Derivative liability, gross liability	(92)	(154)
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Derivative asset, notional amount	10,090	9,028
Derivative liability, notional amount	5,774	4,976
Derivative asset, fair value	137	192
Derivative liability, gross liability	$ (76)	$ (45)