Reportable Segments - Revenue and Total Assets by Geographic Area (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues and total assets by geographic area
% of Revenue	100.00%	100.00%	100.00%
Non-United States
Revenues and total assets by geographic area
% of Revenue	5.80%	2.90%	0.30%
% of total assets	4.40%	2.80%