Schedule II - Valuation and Qualifying Accounts (Details) (Accounts receivable allowance [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts receivable allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 541	$ 740	$ 583
Charged to Costs and Expenses, Additions	34	185	240
Charged to Other Accounts, Additions	0	0	0
Uncollectible Accounts Written-off	110	384	83
Balance at End of Period	$ 465	$ 541	$ 740