Intangible Assets - Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill
Goodwill gross, beginning balance	$ 949,936
Accumulated impairment loss, beginning balance	(197,344)
Goodwill net, beginning balance	752,592
Foreign currency translation adjustments	(22,852)
Goodwill gross, ending balance	927,084
Accumulated impairment loss, ending balance	(197,344)
Goodwill net, ending balance	729,740
North America
Goodwill
Goodwill gross, beginning balance	561,513
Accumulated impairment loss, beginning balance	(7,303)
Goodwill net, beginning balance	554,210
Foreign currency translation adjustments	(4,859)
Goodwill gross, ending balance	556,654
Accumulated impairment loss, ending balance	(7,303)
Goodwill net, ending balance	549,351
Europe & Africa
Goodwill
Goodwill gross, beginning balance	236,992
Accumulated impairment loss, beginning balance	(50,003)
Goodwill net, beginning balance	186,989
Foreign currency translation adjustments	(17,771)
Goodwill gross, ending balance	219,221
Accumulated impairment loss, ending balance	(50,003)
Goodwill net, ending balance	169,218
Australia & New Zealand
Goodwill
Goodwill gross, beginning balance	151,431
Accumulated impairment loss, beginning balance	(140,038)
Goodwill net, beginning balance	11,393
Foreign currency translation adjustments	(222)
Goodwill gross, ending balance	151,209
Accumulated impairment loss, ending balance	(140,038)
Goodwill net, ending balance	$ 11,171