Fair Value - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Nonfinancial Assets and Liabilities [Abstract]
Outstanding balances in impaired loans	$ 52,500		$ 52,500		$ 48,900
Foreclosed assets re-measured after initial recognition			18,400	$ 22,000
Write-downs of allowance for foreclosed assets after initial recognition			1,900	2,600
Noninterest gain (loss) Mortgage banking, net for changes in fair value of LHFS	(1,300)	$ (202)	416,000	3,500
Interest earned on LHFS included in Interest and fees on LHFS and LHFI	1,500	$ 1,400	3,800	$ 3,700
GNMA optional repurchase loans	$ 47,800		$ 47,800		$ 48,200
Maximum [Member]
Nonfinancial Assets and Liabilities [Abstract]
Estimated fair value of financial instruments with immediate and shorter-term maturities			90 days