Debt (Details) (USD $)	12 Months Ended				12 Months Ended					1 Months Ended				1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012 Base rate	Dec. 31, 2012 Base rate Maximum	Dec. 31, 2012 Base rate Minimum	Dec. 31, 2012 Prime rate	Dec. 31, 2012 Federal funds rate	Dec. 31, 2012 LIBOR	Dec. 31, 2012 LIBOR Maximum	Dec. 31, 2012 LIBOR Minimum	Nov. 30, 2011 Term Loan A Facility	Nov. 30, 2012 Delayed Draw Term Loan Facility	Nov. 30, 2011 Delayed Draw Term Loan Facility	Dec. 31, 2012 Credit agreement	Nov. 30, 2011 Revolving Credit Facility	Dec. 31, 2012 Revolving Credit Facility quarter	Nov. 30, 2011 Revolving Credit Facility Letter of credit	Nov. 30, 2011 Revolving Credit Facility Swing line loan
Debt
Maximum borrowing facility										$ 50,000,000		$ 50,000,000		$ 50,000,000		$ 25,000,000	$ 10,000,000
Optional expansion, maximum borrowing capacity														50,000,000
Variable interest rate base (as a percent)		base rate			prime rate	federal funds rate	adjusted LIBOR rate (based on one, two, three or six-month interest periods)
Percentage points added to the reference rate			1.75%	0.75%		0.50%	1.00%	2.75%	1.75%
Number of fiscal quarters used in calculating the consolidated leverage ratio															4
Amount borrowed										50,000,000	50,000,000
Debt issuance cost	1,901,000									1,900,000
Amount outstanding													$ 95,000,000