Derivative Financial Instruments Notional Amounts and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative asset, fair value	$ 193,897	$ 61,688
Derivative liability, gross liability	(105,044)	(47,237)
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	179,038	101,700
Derivative liability, notional amount	5,647	1,646
Derivative asset, fair value	1,722	1,148
Derivative liability, gross liability	(33)	(12)
Forward Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	39,874	1,540
Derivative liability, notional amount	96,000	83,562
Derivative asset, fair value	95	3
Derivative liability, gross liability	(254)	(1,066)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	2,947,777	1,185,144
Derivative liability, notional amount	75,840	1,386,046
Derivative asset, fair value	193,405	33,258
Derivative liability, gross liability	(186)	(30,769)
Interest Rate Swap With Counterparty [Member]
Derivative [Line Items]
Derivative asset, notional amount	75,840	1,386,046
Derivative liability, notional amount	2,947,777	1,185,144
Derivative asset, fair value	186	28,143
Derivative liability, gross liability	(104,544)	(16,338)
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	10,069	5,881
Derivative liability, notional amount	1,691	9,690
Derivative asset, fair value	327	105
Derivative liability, gross liability	(165)	(251)
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Derivative asset, notional amount	4,329	9,220
Derivative liability, notional amount	11,953	6,831
Derivative asset, fair value	208	287
Derivative liability, gross liability	$ (315)	$ (130)