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Stock-Based Compensation - Performance Based Units Earned under Long-Term Incentive Plan (Detail) - Performance stock units
12 Months Ended
Dec. 31, 2016
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Beginning Balance (in shares) | shares 191,536
Vested (in shares) | shares (179,093)
Canceled (in shares) | shares (30,786)
Accrued dividend equivalents (in shares) | shares 2,445
Ending Balance (in shares) | shares 163,967
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]  
Beginning Balance (in dollars per share) $ 34.18
Earned (in dollars per share) 36.76
Vested (in dollars per share) 33.97
Canceled (in dollars per share) 36.65
Accrued dividend equivalents (in dollars per share) 34.02
Ending Balance (in dollars per share) $ 36.77