Receivables (Rollforward of Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts [Roll Forward]
Balance as of beginning of period	$ 2,792	$ 5,852
Current period provision (benefit)	1,243	(332)
Direct write-offs charged against the allowance	(594)	(2,728)
Balance as of end of period	$ 3,441	$ 2,792