Other Financial Information - Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation Allowance [Line Items]
Deductions		$ (5)	$ 0
Allowance for Doubtful Accounts
Valuation Allowance [Line Items]
Balance at Beginning of Period	$ 103	130	166
Additions	336	55	76
Changes in Estimates	(43)	(77)	(112)
Balance at End of Years	$ 396	$ 103	$ 130