Employee Benefit Plans - Additional Information (Detail) - USD ($)				12 Months Ended
	Sep. 09, 2016	May 25, 2016	Nov. 18, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Benefits bases on years of service and compensation, years				5 years
Future defined benefit plan estimated service and interest cost				$ 1,000,000
Future amortization of net loss				3,100,000
Future net periodic pension costs				$ 26,000
Average remaining service period of unrecognized net losses				9 years
Maximum amount of pension plan invested				5.00%
Maximum common stock percentage of market value of investee				5.00%
Maximum period for invested in bonds or notes issued				20 years
Number of equity shares				55,300	55,300
Common stock fair market value				$ 2,400,000	$ 1,700,000
Expected voluntary contribution for the year 2017				5,000,000
Contribution of pension fund				5,750,000	7,500,000	$ 7,500,000
Projected benefit obligations				$ 115,458,000	$ 109,400,000	$ 118,261,000
Eligible employee contributions specified percentage one				3.00%	3.00%	3.00%
Eligible employee contributions specified percentage two				2.00%	2.00%	2.00%
ESOP				$ 0	$ 0	$ 0
Eligibility percentage of employee contributions				100.00%	100.00%	100.00%
Eligibility percentage of employee contributions				50.00%	50.00%	50.00%
Compensation expense for Annual Bonus				$ 1,600,000	$ 1,300,000	$ 1,500,000
Stock options granted to selected participants				96,600
Stock options granted to selected participants exercise price per share				$ 32.37
Options grant expired				7 years
Total intrinsic value of options exercised				$ 1,200,000	600,000
Cash received from stock option exercised				2,500,000	1,400,000
Tax benefit realized from stock options exercised				400,000	200,000
Total intrinsic value of the outstanding shares				3,700,000
Total intrinsic value of the shares exercisable				3,200,000
Your Community Bankshares, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan assets				1,200,000
Projected benefit obligations				$ 1,400,000
Shareholder Return Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares earned by participants			200.00%
Total shareholder return measurement period			3 years
Restricted shares vesting period			3 years
Number of shares granted			12,000	0
KSOP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares held by KSOP				508,066
Total expense for the KSOP/Compensation expense for the stock option component of the Plan				$ 2,800,000	$ 2,500,000	2,200,000
Future issuance under equity compensation plans				445,978	484,430
Equity Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Future issuance under equity compensation plans				117,266	288,541
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total expense for the KSOP/Compensation expense for the stock option component of the Plan				$ 500,000	$ 500,000	400,000
Options grant expired					7 years
Total unrecognized compensation expense related to non-vested stock option grants				$ 200,000
Expense recognition period				1 year
Stock Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options grant expired				10 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total expense for the KSOP/Compensation expense for the stock option component of the Plan				$ 1,400,000	$ 1,200,000	$ 1,000,000
Restricted shares vesting period				36 months
Number of shares granted				76,400
Expense recognition period				1 year 8 months 12 days
Fair value of restricted stock granted				$ 32.45
Total unrecognized compensation expense related to non-vested restricted stock grants				$ 2,700,000
Selected Participants Including Certain Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted to selected participants		96,600
Stock options granted to selected participants exercise price per share		$ 32.37
Pentegra Defined Benefit Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Spinning off of asset cost	$ 3,300,000