Reconciliation of Benefit Obligations and Plan Assets of U.K. Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in benefit obligation:
Projected benefit obligation at beginning of year	$ 40,456	$ 36,882
Interest cost	736	971	$ 939
Actuarial (gains) losses (1)	5,410	3,005
Benefits paid	(1,111)	(1,696)
Foreign currency exchange rate changes	1,709	1,294
Projected benefit obligation at end of year	47,200	40,456	36,882
Accumulated benefit obligation at end of year	47,200	40,456
Change in plan assets:
Fair value of plan assets at beginning of year	38,983	33,124
Actual return on plan assets	5,170	5,410
Employer contributions	988	894
Benefits paid	(1,111)	(1,696)
Foreign currency exchange rate changes	1,659	1,251
Fair value of plan assets at end of year	45,689	38,983	33,124
Funded status at end of year	(1,511)	(1,473)
Amounts included in accumulated other comprehensive loss not yet recognized in net periodic pension cost:
Net actuarial losses at beginning of year	(9,706)	(11,120)
Net actuarial gains (losses) during the year	(1,580)	734
Amounts reclassified from accumulated other comprehensive income to income before income taxes	715	986
Foreign currency exchange rate changes	(387)	(306)
Net actuarial losses	$ (10,958)	$ (9,706)	$ (11,120)