Reconciliation of Benefit Obligations and Plan Assets of U.K. Plan (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in benefit obligation:
Projected benefit obligation at beginning of year		$ 40,329	$ 37,261
Interest cost		939	991	$ 1,232
Actuarial (gains) losses		(1,718)	(27)
Benefits paid		(1,301)	(1,313)
Prior service cost	[1]	754
Foreign currency exchange rate changes		(2,121)	3,417
Projected benefit obligation at end of year		36,882	40,329	37,261
Accumulated benefit obligation at end of year		36,882	40,329
Change in plan assets:
Fair value of plan assets at beginning of year		36,476	31,304
Actual return on plan assets		(1,083)	2,605
Employer contributions		941	887
Benefits paid		(1,301)	(1,313)
Foreign currency exchange rate changes		(1,909)	2,993
Fair value of plan assets at end of year		33,124	36,476	31,304
Funded status at end of year		(3,758)	(3,853)
Amounts included in accumulated other comprehensive loss not yet recognized in net periodic pension cost:
Net actuarial losses at beginning of year		(10,493)	(11,697)
Net actuarial gains (losses) during the year		(1,082)	967
Prior service cost arising during the year	[1]	(754)
Amounts reclassified from accumulated other comprehensive income to income before income taxes		826	1,045
Foreign currency exchange rate changes		383	(808)
Net actuarial loss		(11,120)	(10,493)	$ (11,697)
Amounts expected to be amortized from accumulated other comprehensive loss into net periodic pension cost over the next fiscal year consists of:
Net actuarial loss		959	$ 957
Prior service cost		$ 29

[1] On October 26, 2018, the High Court of Justice in the U.K. ruled that the Guaranteed Minimum Pensions (“GMPs”) provided by pension schemes need to equalize lifetime GMP benefits between genders. In order to meet the requirements set out by the High Court, the Company recorded an estimate of $0.8 million additional benefit obligations based on the existing plan participants, the date the U.K. Plan was allowed to stop accruing additional benefits, the pension plan rules and the approach taken to equalize the benefits. The additional benefit obligation will be amortized and recognized as part of net periodic pension cost in the consolidated statement of operations over the average remaining life expectancy of the plan participants.