Stock-Based Compensation - Assumptions Used to Compute Share-Based Compensation Costs for Stock Options Granted (Detail) (USD $)	6 Months Ended				12 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted average grant-date fair value of stock options					$ 0.63	$ 0.80	$ 1.16
Assumptions
Risk-free interest rate (weighted average)	0.11%	0.14%	0.14%	0.50%	0.60%	0.50%	0.20%
Expected dividend yield
Weighted average expected life (years)	6 months	6 months	6 months	6 months	4 years	4 years	1 year
Volatility (weighted average)	45.00%	74.00%	78.00%	105.00%	68.10%	80.00%	73.00%
Forfeiture rate					11.40%	13.70%