Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Schedule of Restricted Stock Awards (Detail)

v3.3.0.814
Share-Based Compensation - Schedule of Restricted Stock Awards (Detail) - Restricted stock awards [Member] - $ / shares
3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]    
Number of Shares, Restricted stock at beginning of period 193,255 173,222
Number of Shares, Restricted stock granted 2,589 55,773
Number of Shares, Restricted stock vested (41,367) (59,518)
Number of Shares, Restricted stock forfeited (1,350) (16,350)
Number of Shares, Restricted stock at end of period 153,127 153,127
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]    
Weighted-Average Grant Date Fair Value Per Share, Restricted stock at beginning of period (in usd per share) $ 19.22 $ 19.58
Weighted-Average Grant Date Fair Value Per Share, Restricted stock granted (in usd per share) 24.00 22.50
Weighted-Average Grant Date Fair Value Per Share, Restricted stock vested (in usd per share) 17.58 19.08
Weighted-Average Grant Date Fair Value Per Share, Restricted stock forfeited (in usd per share) 17.61 21.49
Weighted-Average Grant Date Fair Value Per Share, Restricted stock at end of period (in usd per share) $ 20.64 $ 20.64
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period   3 years