Stock-Based Compensation - Restricted Stock Activity and Incentive Stock Awards Activity (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding, beginning of period (in dollars per share)		$ 72.18
Granted (in dollars per share)	$ 86.11
Vested (in dollars per share)	70.02
Adjustment for incentive stock awards expected to vest (in dollars per share)	75.43
Canceled (in dollars per share)	$ 74.99
Restricted Stock and Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, beginning of period (in shares)	396,295
Granted (in shares)	153,571
Vested (in shares)	(131,553)
Adjustment for incentive stock awards expected to vest (in shares)	0
Canceled (in shares)	(6,590)
Outstanding, end of period (in shares)	411,723
Incentive Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, beginning of period (in shares)	424,750
Granted (in shares)	157,025
Vested (in shares)	(153,271)
Adjustment for incentive stock awards expected to vest (in shares)	(100,424)
Canceled (in shares)	(5,158)
Outstanding, end of period (in shares)	322,922