Revenues - Changes in Balances of Deferred Costs to Obtain and Fulfill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Deferred Costs to Obtain Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance at beginning of period	$ 1,413
Costs deferred	342
Amortization	(817)
Balance at end of period	938
Deferred Costs to Fulfill Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance at beginning of period	606
Costs deferred	146
Amortization	(423)
Balance at end of period	$ 329