Reconciliation of Benefit Obligations and Plan Assets of U.K. Plan (Details) - UNITED KINGDOM - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligation:
Projected benefit obligation at beginning of year	$ 35,914	$ 39,421
Interest cost	1,232	1,340
Actuarial (gains) losses	7,425	(2,083)
Benefits paid	(809)	(798)
Foreign currency exchange rate changes	(6,501)	(1,966)
Projected benefit obligation at end of year	37,261	35,914
Accumulated benefit obligation at end of year	37,261	35,914
Change in plan assets:
Fair value of plan assets at beginning of year	32,374	33,610
Actual return on plan assets	4,522	342
Employer contributions	868	955
Benefits paid	(809)	(798)
Foreign currency exchange rate changes	(5,651)	(1,735)
Fair value of plan assets at end of year	31,304	32,374
Funded status at end of year	(5,957)	(3,540)
Amounts included in accumulated other comprehensive loss not yet recognized in net periodic pension cost:
Net actuarial losses at beginning of year	(9,874)	(11,890)
Net actuarial gains (losses) during the year	(4,469)	581
Amounts reclassified from accumulated other comprehensive income to income before income taxes	726	875
Foreign currency exchange rate changes	1,920	560
Net actuarial losses at end of year	(11,697)	(9,874)
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	$ 1,148	$ 794