Schedule II-Valuation and Qualifying Accounts - (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts [Abstract]
Allowance for doubtful accounts, Balance at January 1		$ 133	$ 469	$ 377
Allowance for doubtful accounts additions	[1]	91	96	276
Allowance for doubtful accounts, Deductions	[1]	(120)	(432)	(184)
Allowance for doubtful accounts, Balance at December 31		104	133	469
Deferred tax asset valuation allowance, Balance at January 1		2,505	2,650	2,349
Deferred tax asset valuation allowance, Additions	[2]	4,118	469	518
Deferred tax asset valuation allowance, Deductions	[2]	(1,033)	(614)	(217)
Deferred tax asset valuation allowance, Balance at December 31		$ 5,590	$ 2,505	$ 2,650

[1] These balances primarily reflect additions to the allowance charged to expense resulting from the normal course of business, less deductions for recovery of accounts that were previously reserved, and additions and deductions for foreign currency translation

[2] These balances primarily reflect additions or deductions to the valuation allowance associated with the U.S. deferred tax assets, reversal of the valuation allowance against the U.K. and India deferred tax assets, changes in foreign currency exchange rates, and deductions for expiring net operating loss carryforwards