Stock-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Shares
Options outstanding at December 31, 2012 (in shares)			201,000
Options granted (in shares)			0
Options exercised (in shares)	0		(69,000)	0
Options forfeited (in shares)			(1,000)
Options outstanding at June 30, 2013 (in shares)	131,000		131,000
Weighted Average Exercise Price
Options outstanding at December 31, 2012 (usd per share)			$ 3.60
Options granted (usd per share)			$ 0.00
Options exercised (usd per share)			$ 2.84
Options forfeited (usd per share)			$ 2.80
Options outstanding at June 30, 2013 (usd per share)	$ 4.00		$ 4.00
Intrinsic value of options exercised	$ 509,000		$ 579,000
Number Outstanding and Exercisable as of June 30, 2013
Intrinsic value of stock options outstanding	941,000		941,000
Employee Stock Purchase Program Valuation Assumptions
Compensation expense related to options and ESPP rights	1,583,000	1,895,000	2,887,000	4,469,000
Restricted Stock
Restricted Stock
Unvested as of December 31, 2012 (in shares)			1,539,000
Granted (in shares)			1,260,000
Vested (shares)			(440,000)
Forfeited (shares)			(169,000)
Unvested as of June 30, 2013 (in shares)	2,190,000		2,190,000
Weighted Average Grant Date Fair Value (per share)
Unvested, Beginning Balance (usd per share)			$ 9.38
Granted (usd per share)			$ 9.34	$ 9.01
Vested (usd per share)			$ 8.99
Forfeited (usd per share)			$ 9.46
Unvested, Ending Balance (usd per share)	$ 9.43		$ 9.43
Fair value of equity instrument other than options			4,000,000	4,300,000
Shares of restricted stock repurchased to satisfy tax withholding obligations			176,689	175,321
Aggregate intrinsic value of restricted shares	24,500,000		24,500,000
Total unrecognized compensation cost related to non-vested restricted shares	13,100,000		13,100,000
Total unrecognized compensation cost, weighted-average recognition period			1 year 21 months 24 days
Employee Stock Purchase Program Valuation Assumptions
Compensation expense related to options and ESPP rights	1,600,000	1,900,000	2,900,000	4,500,000
Options and ESPP
Weighted Average Grant Date Fair Value (per share)
Granted (usd per share)			$ 1.98	$ 1.93
Fair value of equity instrument other than options			29,000	46,000
Employee Stock Purchase Program Valuation Assumptions
Compensation expense related to options and ESPP rights	20,000	19,000	38,000	12,000
Cash received from exercise of options and ESPP			341,000	144,000
ESPP
Employee Stock Purchase Program Valuation Assumptions
Expected term			6 months	6 months
Risk-free rate			0.11%	0.15%
Expected volatility			19.90%	29.40%
Dividend yield			0.00%	0.00%
$4.00
Weighted Average Exercise Price
Lower Range of Exercise Price			$ 4.00
Upper Range of Exercise Price			$ 4.00
Number Outstanding and Exercisable as of June 30, 2013
Number outstanding (shares)	131,000		131,000
Weighted Average Remaining Contractual Life (in years)			11 months 25 days
Weighted Average Exercise Price (usd per share)	$ 4.00		$ 4.00
Employee Stock Purchase Plan 2009
Weighted Average Grant Date Fair Value (per share)
Shares issued under the ESPP			20,170	19,823
Employee Stock Purchase Plan 2009 | ESPP
Weighted Average Grant Date Fair Value (per share)
Total unrecognized compensation cost, weighted-average recognition period			1 month
ESPP, purchase price (usd per share)	$ 7.11	$ 7.00	$ 7.11	$ 7.00
Employee Stock Purchase Program Valuation Assumptions
Intrinsic value of shares purchased ESPP			29,000
Intrinsic value of rights outstanding ESPP			34,000
Unrecognized compensation cost related to non-vested stock options	$ 7,000		$ 7,000