Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of shares, Beginning Balance | shares	302,824
Number of shares, Granted | shares	274,392
Number of shares, Forfeited | shares	(29,134)
Number of shares, Settled | shares	(78,423)
Number of shares, Ending Balance | shares	469,659
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, Beginning Balance (in $ per share) | $ / shares	$ 111.56
Weighted Average Grant Date Fair Value, Granted (in $ per share) | $ / shares	108.25
Weighted Average Grant Date Fair Value, Forfeited (in $ per share) | $ / shares	121.06
Weighted Average Grant Date Fair Value, Settled (in $ per share) | $ / shares	140.86
Weighted Average Grant Date Fair Value, Ending Balance (in $ per share) | $ / shares	$ 104.14