Stock-Based Compensation - Assumptions Used for Estimating Fair Value of Employee Stock Options (Detail) - Employee Stock Option [Member]	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield of stock	0.00%		0.00%
Expected volatility			0.88%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.46%	1.60%	1.50%
Expected life of option (in years)	5 years 3 months	5 years 3 months 11 days	5 years 4 months 10 days
Expected volatility	0.66%	0.66%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.58%	1.70%	1.88%
Expected life of option (in years)	5 years 3 months 22 days	5 years 3 months 29 days	5 years 4 months 17 days
Expected volatility	0.67%	0.69%