Revolving Credit Facility (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]
Borrowings outstanding under revolving credit facility	$ 0	$ 0
Fees associated with unused portion of committed amount	0
Actual net worth for compliance	161,900,000
Minimum net worth required for compliance	95,000,000
Ratio of total liability to net worth	0.36
Maximum ratio of total liability to net worth for compliance	2
Actual working capital for compliance	66,000,000
Minimum working capital for compliance	40,000,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum borrowings	30,000,000.0
Standby letter of credit	900,000
Borrowings available under the revolving credit facility	$ 29,100,000
Frequency of periodic payment	monthly
Description of variable rate basis	LIBOR
Stated percentage	2.50%
Weighted average interest rate	2.69%	2.80%