Debt (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit agreement term	4 years
Current borrowing capacity	$ 100,000,000
Maximum borrowing capacity	125,000,000
Outstanding balance on the line of credit		45,000,000
Interest rate on the outstanding balance		2.00%
Interest expense incurred	0	576,000
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	20,000,000
Swing Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 5,000,000