Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017 USD ($) Office Factor Region	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of offices | Office		198
Percentage of outstanding principal to be repurchased under GNMA optional repurchase program		100.00%
Number of days to pass to be classified as past due LHFI		30 days
Balance of commercial nonaccrual loans identified for impairment analysis, minimum		$ 500,000
Components in allowance for loan losses methodology | Factor		3
Key market regions | Region		5
Finite-lived intangible assets, average useful life		20 years
Securities with limited marketability		$ 67,700,000	$ 71,000,000
Effective income tax rate		35.00%	35.00%	35.00%
Amount be reclassified from AOCI to retained earnings		$ 8,500
Excess tax expense from stock-based compensation arrangements being reclassified from financing activities to other operating activities, net			$ 107,000	$ 211,000
Taxes paid for shares directly withheld being reclassified from other operating activities, net to financing activities		1,724,000	$ 1,017,000	$ 863,000
Total outstanding operating lease obligation		67,863,000
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Total outstanding operating lease obligation		$ 67,900
Percentage of total outstanding operating lease obligation of total assets		0.50%
Accounting Standards Update 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative adjustment		$ 0
Percentage of revenues earned		23.00%
Scenario Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
Effective income tax rate	21.00%
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Summary Of Significant Accounting Policies [Line Items]
Description of variable rate basis for derivative		three-month LIBOR
Period for which cash flow hedges will be used to hedge quarterly interest payments		5 years
Derivative inception date		Dec. 31, 2014
Derivative maturity date		Dec. 31, 2019
Credit Card Loans [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due loans are to be charged-off		180 days
Commercial Credits [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due for loan to be classified as nonaccrual		90 days
Non-Business Purpose Credits [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due for loan to be classified as nonaccrual		120 days
Number of days past due loans are to be charged-off		120 days
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days mortgage LHFS are retained on balance sheet		30 days
Minimum [Member] | Furniture and Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets		3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days mortgage LHFS are retained on balance sheet		45 days
Period for which cash flow hedges will be used to hedge quarterly interest payments		90 days
Maximum [Member] | Buildings [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets		39 years
Maximum [Member] | Furniture and Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets		10 years
Maximum [Member] | 1-4 Family Residential Real Estate [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due loans are to be charged-off		180 days