Stock-based Compensation - Summary of Restricted Stock Units Activity (Detail) - Restricted Stock Units [Member]	9 Months Ended
	Sep. 30, 2015 $ / 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	179,936
Number of shares, Granted | shares	116,295
Number of shares, Forfeited | shares	(493)
Number of shares, Settled | shares	(87,410)
Number of shares, Ending Balance | shares	208,328
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)	$ 143.25
Weighted Average Grant Date Fair Value, Granted (in $ per share)	134.46
Weighted Average Grant Date Fair Value, Forfeited (in $ per share)	175.16
Weighted Average Grant Date Fair Value, Settled (in $ per share)	102.00
Weighted Average Grant Date Fair Value, Ending Balance (in $ per share)	$ 155.57