Benefit Plans - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) retirement_payment $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares	Dec. 31, 2006	Dec. 31, 2002
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan age attained for coverage	21 years
Service period for employees of coverage age, years	1 year
Vesting percentage of participants in pension plan	100.00%
Lump sum payment	$ 4,300,000
Lump sum pension distribution	$ 1,300,000
Requisite service period for deferred compensation arrangement	10 years			10 years	10 years
Number of quarterly payments made to Board of Directors from Retirement Plan | retirement_payment	40
Discount rate	4.50%
Percentage of matching contribution		25.00%	25.00%
Percentage of contribution made by the participants in benefit plans		6.00%	6.00%
Retirement plan for the board of directors to get maximum payments minimum age	72 years
Benefit plans compensation expense	$ 1,250
Period in which undistributed balance of accrued benefit will be distributed	60 days
Shares purchased under ESOP | shares	4,769,464
Average price per share purchased under ESOP (in dollars per share) | $ / shares	$ 17.09
Outstanding loan principal	$ 49,900,000
Number of shares released under ESOP | shares	209,631	201,512
Unallocated ESOP shares held in suspense | shares	2,442,414
Fair market value of ESOP shares	$ 49,200,000
ESOP compensation expenses	2,997,000	$ 2,654,000	$ 2,559,000
Estimated expense under the supplemental ESOP provision	$ 54,000	48,000	45,000
Number of shares authorized for issuance under stock award plan | shares	3,686,510
Limited number of shares authorized for issuance | shares	2,100,000
Unrecognized compensation cost relating go unvested restricted stock	$ 1,800,000
Weighted average period in which unrecognized compensation cost recognized years	2 years 1 month 6 days
Fair value of options vesting	$ 274,000	$ 438,000	$ 696,000
Projected share based compensation expense, 2016	130,000
Projected share based compensation expense, 2017	96,000
Projected share based compensation expense, 2018	21,000
Aggregate intrinsic value of stock options outstanding	5,720,000
Aggregate intrinsic value of stock options exercisable	$ 4,703,000
Weighted average fair value of options granted (in dollars per share) | $ / shares	$ 2.52	$ 1.64	$ 3.49
Retirement Plan for the Board of Directors [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) in other comprehensive income from retirement plans	$ (2,000)	$ 7,000	$ 6,000
Restricted Stock [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Share based payment award vesting period in years	3 years
Restricted Stock [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Share based payment award vesting period in years	5 years
Outstanding Stock Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Share based payment award compensation expense	$ 4,625,000	6,359,000	4,869,000
Stock Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Share based payment award vesting period in years	5 years
Share based payment award expiration period in years	10 years
Share based payment award compensation expense	$ 272,000	298,000	297,000
Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Share based payment award vesting period in years	3 years
401(k) Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of matching contribution	25.00%
Percentage of contribution made by the participants in benefit plans	6.00%
Contribution to the Plan	$ 770,000	674,000	587,000
Estimated expense of supplemental ESOP provision	12,000	11,000	7,000
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate contributions to the benefit plan	93,000	102,000	162,000
Increase (decrease) in other comprehensive income from retirement plans	(82,000)	198,000	(56,000)
Other Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Retirement plan liabilities	2,110,000	2,166,000
Other Liabilities [Member] | Retirement Plan for the Board of Directors [Member]
Defined Benefit Plan Disclosure [Line Items]
Retirement plan liabilities	158,000	169,000
Board of Directors [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit plans compensation expense	15,000	15,000	15,000
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Lump sum pension distribution	0	1,336,000	0
Actuarial gain (loss) during the period	(78,000)	(51,000)	(114,000)
Defined benefit plan, funded status of plan	$ 13,174,000	$ 13,823,000	$ 16,597,000
Discount rate	4.50%	4.00%	5.00%
Contribution to the Plan	$ 0	$ 0	$ 0
Post-retirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Lump sum pension distribution	0	0	0
Actuarial gain (loss) during the period	(122,000)	(51,000)	210,000
Defined benefit plan, funded status of plan	$ (25,694,000)	$ (28,333,000)	$ (22,086,000)
Discount rate	4.50%	4.00%	5.00%
Contribution to the Plan	$ 644,000	$ 670,000	$ 624,000
Share-based Compensation Award, Tranche One [Member] | Outstanding Stock Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Share based payment award vesting period in years	2 years
Share-based Compensation Award, Tranche Two [Member] | Outstanding Stock Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Share based payment award vesting period in years	3 years
Other Comprehensive Income (Loss) [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss) during the period		(1,500,000)
Other Comprehensive Income (Loss) [Member] | Post-retirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss) during the period		$ (3,000,000)