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Stock-Based Compensation - Assumptions Used to Compute Share-Based Compensation Costs for Stock Options Granted (Detail) - $ / shares
6 Months Ended 12 Months Ended
Sep. 30, 2016
Mar. 31, 2016
Sep. 30, 2015
Mar. 31, 2015
Sep. 30, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]                
Weighted average grant-date fair value of stock options           $ 1.40 $ 3.08 $ 2.28
Assumptions                
Risk-free interest rate (weighted average) 0.47% 0.18% 0.11% 0.40% 0.80% 1.10% 1.10% 1.20%
Weighted average expected life (years) 6 months 6 months 6 months 6 months 6 months 4 years 9 months 18 days 4 years 3 years 6 months
Volatility (weighted average) 40.40% 66.10% 103.80% 109.10% 74.00% 74.30% 83.50% 82.90%
Forfeiture rate           23.00% 23.30% 25.50%