Stock-Based Compensation (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2010 Rollover Options	Dec. 31, 2010 Rollover Options	Dec. 31, 2012 Tranche 1 and 2	Dec. 31, 2012 Tranche 3	Dec. 31, 2012 2009 Management Equity Plan	Dec. 31, 2011 2009 Management Equity Plan	Dec. 31, 2010 2009 Management Equity Plan	Dec. 31, 2012 2009 Management Equity Plan Options	Dec. 31, 2012 2009 Management Equity Plan Tranche 1 and 2	Dec. 31, 2012 2009 Management Equity Plan Tranche 3	Dec. 31, 2012 2009 Management Equity Plan Option Tranches item
Stock-Based Compensation
Number of shares of the common stock of Holdings reserved for issuance								1,102,500
Vesting period			5 years
Vesting period for service				5 years							5 years
Contractual term of options granted	10 years							10 years
Number of tranches											3
Percentage of the award vesting on each anniversary									20.00%
Percentage of the award vesting based on service period on each anniversary					20.00%
Exercise price of outstanding options, minimum (in dollars per share) that were exercised	$ 15.31
Exercise price of outstanding options, maximum (in dollars per share) that were exercised	$ 15.75
Options granted (in shares)	224,210				22,610	236,829	409,710
Exercise price (in dollars per share)	$ 22.82
Recognized compensation cost		$ 1,500,000			$ 1,100,000	$ 1,600,000	$ 3,200,000			$ 0
Unrecognized compensation cost			$ 1,500,000	$ 900,000				$ 2,400,000
Expected weighted-average period of recognition of unrecognized compensation cost								2 years 6 months