Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Commitments [Line Items]
Rent expense	$ 13,600	$ 11,400	$ 10,700
Proceeds from sale-leaseback transactions	0	0	$ 2,017
Term of lease			7 years
Deferred credits	2,400	2,500
Property, plant, and equipment grants from Ireland	147	170	$ 171
Irish grants refundable if operations discontinued	$ 3,000
Remaining grant liability period	1 year
Royalty expense	$ 4,400	$ 3,200	$ 2,700
Minimum
Other Commitments [Line Items]
Grant period	5 years
Maximum
Other Commitments [Line Items]
Grant period	8 years