Accumulated Other Comprehensive Loss - Narrative (Details) - USD ($)	3 Months Ended					12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss)						$ (10,528,000)	$ (33,009,000)	$ 39,531,000
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss)	$ (2,200,000)	$ 2,100,000	$ (200,000)	$ (5,100,000)	$ 5,400,000		$ 2,200,000