Credit Facilities (Details) (Revolving Credit Facility, USD $)	Dec. 31, 2014 letter_of_credit
LIBOR Rate Loan
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 35,000,000
Credit facility, interest rate on outstanding balance	3.30%
Standby letters of credit, total amount outstanding	1,500,000
Number of standby letters of credit outstanding	6
Sixth Amendment
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 15,000,000.00