Accounts Receivable and Allowance for Doubtful Accounts - Changes in Allowance for Doubtful Accounts related to Long-Term Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Balance, Beginning of Period	$ 0	$ 392	$ 1,621
Bad Debt Recovery	0	(392)	(1,229)
Balance, End of Period	$ 0	$ 0	$ 392