Segment Information - Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	$ 1,784,081	$ 1,862,716
North America
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	1,135,065	1,175,154
Europe And Africa
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	535,665	579,879
Australia And New Zealand
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	66,086	75,095
Corporate Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	$ 47,265	$ 32,588