Share-Based Compensation - Key Assumptions Used to Apply the Black-Scholes Option Pricing Model (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Average risk-free interest rate	1.64%	1.17%
Expected life of option grants	5 years	5 years
Expected volatility of underlying stock	72.55%	99.00%
Expected dividend payment rate, as a percentage of the share price on the date of grant	0.89%	0.82%
Weighted average grant date fair value	$ 10.20	$ 13.80