Employee Benefit Plans - Unrecognized Compensation Expense Under Equity-Based Compensation Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Unrecognized Stock Based Compensation Expense [Line Items]
Unrecognized equity-based compensation expense	$ 17,131
Stock Options [Member]
Unrecognized Stock Based Compensation Expense [Line Items]
Unrecognized equity-based compensation , Weighted-Average Vesting Period (in years)	3 years 4 months 24 days
Unrecognized equity-based compensation expense	15,809
Restricted Stock [Member]
Unrecognized Stock Based Compensation Expense [Line Items]
Unrecognized equity-based compensation , Weighted-Average Vesting Period (in years)	3 years 6 months
Unrecognized equity-based compensation expense	$ 1,322