Shareholders' Equity - Components Of Accumulated OCI (Details) - USD ($) $ in Thousands	Jan. 01, 2018	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative foreign currency translation adjustment		$ (57,998)	$ (62,689)
Unrealized loss on hedges, net of tax		(6,159)	(7,507)
Unrealized gain on note receivable, net of tax		0	409
Accumulated other comprehensive loss		(64,157)	(69,787)
Deferred tax assets		$ 1,600	4,000
Deferred tax liabilities			$ 200
Retained Earnings | ASU No. 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of stranded tax benefits (losses)	$ 1,500
Accumulated OCI | ASU No. 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of stranded tax benefits (losses)	(1,500)
Hedges | Retained Earnings | ASU No. 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of stranded tax benefits (losses)	1,600
Hedges | Accumulated OCI | ASU No. 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of stranded tax benefits (losses)	(1,600)
Note Receivable | Retained Earnings | ASU No. 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of stranded tax benefits (losses)	(100)
Note Receivable | Accumulated OCI | ASU No. 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of stranded tax benefits (losses)	$ 100