Receivables (Rollforward of Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts [Roll Forward]
Balance as of beginning of period	$ 5,852	$ 6,039
Current period provision	(291)	796
Direct write-offs charged (reversals) against the allowance	(530)	(983)
Balance as of end of period	$ 5,031	$ 5,852