Debt Revolving Credit Agreement (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 21, 2014	Dec. 15, 2011
Debt Instrument [Line Items]
Interest Income, Other	$ 81	$ 35	$ 222
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					125,000	100,000
Aggregate principal amount available for a Canadian subfacility	20,000
Aggregate principal amount available for letters of credit	20,000
Aggregate principal amount available for swingline loans	10,000
Maturity date	Dec. 10, 2019			Dec. 15, 2015
Weighted average interest rate for borrowings	3.08%	2.71%	2.71%
Line of Credit, Terms, Provision to Increase the Aggregate Amount of Commitments Under Certain Conditions, Amount	25,000			50,000
Credit Facility Incremental Commitment					25,000
Line of Credit Facility, Maximum Borrowing Capacity before triggering cash dominion	100,397
Line of Credit Facility, Remaining Unrestricted Borrowing Capacity	41,197
Minimum | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Customary base rate plus an applicable margin percentage	0.50%
Adjusted LIBOR rate plus an applicable margin	1.50%
Ratio of EBITDA to fixed charges	1.1
Excess availability as a percentage of calculated borrowing base to require fixed charge coverage ratio	10.00%
Excess availability to require fixed charge coverage ratio	12,500
Excess availability as a percentage of calculated borrowing base before cash dominion	12.50%
Excess availability before cash dominion	$ 15,625
Maximum | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Customary base rate plus an applicable margin percentage	1.00%
Adjusted LIBOR rate plus an applicable margin	2.00%