Segment Reporting - (Percentage of Revenue by Geographic Area) (Details) - Geographic Concentration Risk - Total Revenue	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Concentration Risk [Line Items]
Revenues, percentage by country	100.00%	100.00%	100.00%	100.00%
North America
Concentration Risk [Line Items]
Revenues, percentage by country	54.00%	49.00%	51.00%	47.00%
Europe
Concentration Risk [Line Items]
Revenues, percentage by country	33.00%	39.00%	37.00%	41.00%
APAC
Concentration Risk [Line Items]
Revenues, percentage by country	13.00%	12.00%	12.00%	12.00%
Non-US [Member]
Concentration Risk [Line Items]
Revenues, percentage by country	0.00%	0.00%	0.00%	0.00%