Assumptions Used in Determining Fair Value of RSU Awards Granted (Detail) - Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Line Items]
Grant date fair value	$ 7.02	$ 7.53
Grant date closing stock price	6.74	$ 11.05
Grant date closing index value	$ 4,941.53
Volatility	48.66%	48.90%
Risk-free rate	0.85%	0.84%
Probability of death or disability		5.00%