Senior Credit Facility (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Feb. 01, 2012 Years
Senior Credit Facility [Abstract]
Senior credit facility amount		$ 150,000,000
Line of Credit Facility Term, In Years		5
Base reference rate of credit facilities	LIBOR
Interest rate spread above LIBOR as of reporting period (in hundredths)	1.10%
Debt Instrument, Interest Rate, Effective Percentage	1.30%
Letters of Credit Outstanding, Amount	11,266
Available borrowing capacity	$ 138,734