Intangible Assets - Goodwill and Net Carrying Amounts (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill
Goodwill gross, beginning balance	$ 964,980
Accumulated impairment loss, beginning balance	(190,041)
Goodwill net, beginning balance	774,939
Foreign currency translation adjustments	4,455
Goodwill gross, ending balance	969,435
Accumulated impairment loss, ending balance	(190,041)
Goodwill net, ending balance	779,394
Trade Name
Intangible Assets
Indefinite lived intangible asset, Beginning balance	659
Indefinite lived intangible asset, foreign currency translation adjustments	18
Indefinite lived intangible asset, Ending balance	677
North America
Goodwill
Goodwill gross, beginning balance	565,717
Goodwill net, beginning balance	565,717
Foreign currency translation adjustments	(3,102)
Goodwill gross, ending balance	562,615
Goodwill net, ending balance	562,615
North America | Trade Name
Intangible Assets
Indefinite lived intangible asset, Beginning balance	200
Indefinite lived intangible asset, Ending balance	200
Europe And Africa
Goodwill
Goodwill gross, beginning balance	246,549
Accumulated impairment loss, beginning balance	(50,003)
Goodwill net, beginning balance	196,546
Foreign currency translation adjustments	7,761
Goodwill gross, ending balance	254,310
Accumulated impairment loss, ending balance	(50,003)
Goodwill net, ending balance	204,307
Europe And Africa | Trade Name
Intangible Assets
Indefinite lived intangible asset, Beginning balance	459
Indefinite lived intangible asset, foreign currency translation adjustments	18
Indefinite lived intangible asset, Ending balance	477
Australia And New Zealand
Goodwill
Goodwill gross, beginning balance	152,714
Accumulated impairment loss, beginning balance	(140,038)
Goodwill net, beginning balance	12,676
Foreign currency translation adjustments	(204)
Goodwill gross, ending balance	152,510
Accumulated impairment loss, ending balance	(140,038)
Goodwill net, ending balance	$ 12,472