Stock Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2010	Dec. 31, 2012
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Expected dividend yield	0.00%			0.00%
Compensation expense (income)			$ 2,245,000	$ 2,678,000
Options exercised, total intrinsic value			4,200,000
Total amount of cash received from exercise of options			8,100,000
Employee stock purchase plan, number of offering			2
Employee stock purchase plan, offering period			6 months
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term				5 years 10 months 25 days
Expected volatility				47.70%
Stock options, expected dividend yield				1.43%
Employee Stock Purchase Plan [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Compensation expense (income)	100,000	100,000	200,000	200,000
Employee stock purchase plan, purchase price discount			15.00%
Stock Options [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock options, contractual term			10 years
Expected dividend yield			0.00%
Stock-based compensation, approximate forfeitures rate	3.00%
Stock Option [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Compensation expense (income)	200,000	600,000	600,000	1,300,000
Performance-Based Restricted Stock [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Compensation expense (income)	200,000	500,000	200,000	400,000
Restricted stock award program, measurement period					three
Restricted stock award program, payment of award as percentage of target						200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	3 years
Expected volatility	37.10%
Stock options, expected dividend yield	0.40%
Performance-Based Restricted Stock [Member] | Minimum [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Restricted stock award program, awarded shares as a percentage of the original award amount					0.00%
Performance-Based Restricted Stock [Member] | Maximum [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Restricted stock award program, awarded shares as a percentage of the original award amount					200.00%
Time Based Restricted Stock [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Compensation expense (income)	300,000	400,000	600,000	900,000
Restricted stock award program, vesting period			3 years
Deferred Stock Units [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Compensation expense (income)	$ 700,000	$ 700,000	$ 700,000	$ 700,000