Employee Savings Plan - Additional Information (Detail) (USD $)	12 Months Ended			15 Months Ended
	Dec. 31, 2012 Y	Dec. 31, 2011	Dec. 31, 2010	Jul. 04, 2010
Employee Benefit Plans [Line Items]
Minimum age to be eligible to defined contribution plan	21
Maximum part of pre tax salary which employee can contribute to define contribution plan	25.00%
Company contribution per dollar of employee contribution	$ 0.50			$ 0.25
Maximum contribution by company expressed as percentage of employee pre-tax salary	3.00%			1.50%
Company contributions vest at end of two years	20.00%
Company contributions vest at end of three years	40.00%
Company contributions vest at end of four years	60.00%
Company contributions vest at end of five years	100.00%
Defined Contribution Plan, Cost Recognized	$ 1,362,000	$ 1,218,000	$ 776,000