Summary of Operations and Significant Accounting Policies - Component of Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Unrealized foreign currency losses	$ (64,553)	$ (42,010)
Unrealized gain on interest rate swap, net of tax	3,261	2,524
Unrealized loss on defined benefit plan	$ (40,554)	$ (43,994)

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant