Segment Information - Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	$ 1,894,508	$ 1,862,716
North America
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	1,208,694	1,175,154
Europe And Africa
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	591,678	579,879
Australia And New Zealand
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	70,261	75,095
Corporate Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Total identifiable assets	$ 23,875	$ 32,588