Derivative Financial Instruments Notional Amounts and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative asset, fair value	$ 368,346	$ 144,371
Derivative liability, gross liability	(180,834)	(76,067)
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	315,084	132,260
Derivative liability, notional amount	4,968	9,783
Derivative asset, fair value	5,990	1,123
Derivative liability, gross liability	(57)	(53)
Forward Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	0	75,000
Derivative liability, notional amount	341,680	180,000
Derivative asset, fair value	0	63
Derivative liability, gross liability	(4,131)	(371)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	3,457,081	2,903,489
Derivative liability, notional amount	(12,288)	376,705
Derivative asset, fair value	368,172	143,484
Derivative liability, gross liability	(6)	(695)
Interest Rate Swap With Counterparty [Member]
Derivative [Line Items]
Derivative asset, notional amount	12,288	376,705
Derivative liability, notional amount	3,457,081	2,903,489
Derivative asset, fair value	6	695
Derivative liability, gross liability	(180,576)	(75,327)
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	12,331	3,373
Derivative liability, notional amount	2,985	7,283
Derivative asset, fair value	359	38
Derivative liability, gross liability	(125)	(154)
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Derivative asset, notional amount	5,290	9,028
Derivative liability, notional amount	11,393	4,976
Derivative asset, fair value	168	192
Derivative liability, gross liability	$ (252)	$ (45)