Derivative Financial Instruments Notional Amounts and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative asset, fair value	$ 48,003	$ 41,636
Derivative liability, fair value	(41,625)	(41,842)
Derivative asset (liability), net	7,592	2,824
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	141,250	87,119
Derivative liability, notional amount	5,530	18,239
Derivative asset, fair value	1,283	863
Derivative liability, fair value	(16)	(227)
Derivative asset (liability), net	1,267	636
Forward Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	27,562	70,031
Derivative liability, notional amount	77,000	19,964
Derivative asset, fair value	48	2,223
Derivative liability, fair value	(207)	(112)
Derivative asset (liability), net	(159)	2,111
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	1,329,394	876,744
Derivative liability, notional amount	578,120	583,060
Derivative asset, fair value	34,028	24,397
Derivative liability, fair value	(13,682)	(16,998)
Derivative asset (liability), net	20,346	7,399
Interest Rate Swap With Counterparty [Member]
Derivative [Line Items]
Derivative asset, notional amount	578,120	583,060
Derivative liability, notional amount	1,329,394	876,744
Derivative asset, fair value	13,682	16,998
Derivative liability, fair value	(27,663)	(24,397)
Derivative asset (liability), net	(13,981)	(7,399)
Centrally Cleared Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Derivative liability, notional amount	324,300
Derivative liability, fair value	0
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	5,912	11,674
Derivative liability, notional amount	5,473	4,659
Derivative asset, fair value	332	504
Derivative liability, fair value	(226)	(221)
Derivative asset (liability), net	106	283
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Derivative asset, notional amount	8,978	7,040
Derivative liability, notional amount	4,420	12,869
Derivative asset, fair value	293	241
Derivative liability, fair value	(280)	(447)
Derivative asset (liability), net	$ 13	$ (206)