Stock-Based Compensation Plans - Summarizes Transactions of SEUs (Detail) - Stock Equivalent Units [Member]	9 Months Ended
	Sep. 30, 2016 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Number of SEUs, Beginning balance | shares	279,750
Granted at discount, Number of SEUs | shares	70,153
Granted at market value, Number of SEUs | shares	7,316
Exercised, Number of SEUs | shares	(49,623)
Forfeited, Number of SEUs | shares	(8,980)
Outstanding, Number of SEUs, Ending balance | shares	298,616
Outstanding, Weighted Average Exercise Price, Beginning balance	$ 3.79
Granted at discount, Weighted Average Exercise Price	0.00
Granted at market value, Weighted Average Exercise Price	44.18
Exercised, Weighted Average Exercise Price	1.74
Forfeited, Weighted Average Exercise Price	4.41
Outstanding, Weighted Average Exercise Price, Ending balance	4.21
Outstanding, Weighted Average Grant-Date Fair Value	31.72
Granted at discount, Weighted Average Grant-Date Fair Value	36.56
Granted at market value, Weighted Average Grant-Date Fair Value	9.11
Exercised, Weighted Average Grant-Date Fair Value	27.79
Forfeited, Weighted Average Grant-Date Fair Value	30.73
Outstanding, Weighted Average Grant-Date Fair Value	$ 32.99