Segment Information - Narrative (Details) - Segment	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Number of reportable segments	7
Percentage of consolidated revenues not exceeded by any single customer	5.00%	5.00%	5.00%
Germany
Segment Reporting Information [Line Items]
Percentage of long-lived asset owned		10.00%
Non-US
Segment Reporting Information [Line Items]
Percentage of long-lived asset owned	10.00%		10.00%