Derivative Financial Instruments Notional Amounts and Fair Values of Derivative Financial Instruments (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative asset, fair value	$ (66,020,000)	$ (43,630,000)
Derivative liability, fair value	(75,146,000)	(38,997,000)
Derivative asset (liability), net	(7,902,000)	5,611,000
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	143,869,000	129,469,000
Derivative liability, notional amount	11,535,000	8,957,000
Derivative asset, fair value	(904,000)	(1,059,000)
Derivative liability, fair value	(77,000)	(59,000)
Derivative asset (liability), net	827,000	1,000,000
Forward Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	122,856,000	3,856,000
Derivative liability, notional amount	0	100,808,000
Derivative asset, fair value	(480,000)	(34,000)
Derivative liability, fair value	0	(213,000)
Derivative asset (liability), net	480,000	(179,000)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	548,277,000	1,316,548,000
Derivative liability, notional amount	1,882,655,000	716,634,000
Derivative asset, fair value	(6,922,000)	(24,505,000)
Derivative liability, fair value	(71,175,000)	(18,978,000)
Derivative asset (liability), net	(64,253,000)	5,527,000
Interest Rate Swap With Counterparty [Member]
Derivative [Line Items]
Derivative asset, notional amount	1,882,655,000	716,634,000
Derivative liability, notional amount	548,277,000	1,316,548,000
Derivative asset, fair value	(58,773,000)	(18,941,000)
Derivative liability, fair value	(3,778,000)	(19,764,000)
Derivative asset (liability), net	54,995,000	(823,000)
Centrally Cleared Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Derivative liability, fair value	0	0
Derivative Asset, Collateral, Obligation to Return Cash, Offset	9,300,000
Derivatives variation margin		4,600,000
Centrally Cleared Interest Rate Swap with Counterparty [Member] | Positive Fair Values [Member]
Derivative [Line Items]
Derivative asset, notional amount	416,100,000	24,400,000
Derivative asset, fair value	0	0
Centrally Cleared Interest Rate Swap with Counterparty [Member] | Negative Fair Values [Member]
Derivative [Line Items]
Derivative liability, notional amount	249,700,000	377,100,000
Derivative liability, fair value	0	0
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	8,797,000	4,852,000
Derivative liability, notional amount	9,176,000	5,914,000
Derivative asset, fair value	(193,000)	(276,000)
Derivative liability, fair value	(277,000)	(119,000)
Derivative asset (liability), net	(84,000)	157,000
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Derivative asset, notional amount	10,506,000	7,960,000
Derivative liability, notional amount	9,239,000	6,048,000
Derivative asset, fair value	(325,000)	(184,000)
Derivative liability, fair value	(192,000)	(255,000)
Derivative asset (liability), net	$ 133,000	$ (71,000)