Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Computed federal income tax expense at applicable statutory rate									$ 10,399	$ 12,559	$ 8,885
State income taxes									(59)	279	193
Tax credits									(1,734)	(1,377)	(1,164)
Production activity deduction									0	0	(53)
Foreign tax rate differential									(1,361)	(3,329)	(3,717)
Uncertain tax positions									267	(19)	597
Deferred compensation insurance assets									186	(479)	(307)
Transaction-related expenses									223	90	274
U.S. transition tax									(3,271)	10,612	0
TCJA remeasurement of deferred taxes									(71)	(8,383)	0
Stock-based payments									(4,278)	(2,264)	0
Bargain purchase gain									0	(1,570)	0
In-process research and development									0	1,486	0
Net GILTI									347	0	0
Foreign withholding tax									5,590	0	0
Other — including the effect of graduated rates									1,264	753	557
Total income tax expense	$ 3,022	$ 2,766	$ 624	$ 1,090	$ 4,474	$ 1,364	$ 1,830	$ 690	$ 7,502	$ 8,358	$ 5,265