Employee Benefit Plans - Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Change in Benefit Obligation:
Benefit obligation at beginning of period	$ 90,051	$ 91,875
Additional obligation due to acquisition		5,631
Service cost	80	82
Interest cost	2,448	2,350
Actuarial loss	9,168	(4,356)
Plan amendments	(835)	1,334
Benefits paid	(3,082)	(1,558)
Foreign-exchange rate changes	3,131	(5,307)
Benefit obligation at end of year	100,961	90,051
Change in Plan Assets:
Fair value of plan assets at beginning of period	62,952	64,886
Additional obligation due to acquisition		2,184
Actual return on plan assets	10,906	(1,432)
Employer contributions	2,557	2,477
Benefits paid	(2,995)	(1,421)
Foreign-exchange rate changes	2,455	(3,742)
Fair value of plan assets at end of period	75,875	62,952
Funded status at end of year			$ (25,086)				$ (27,099)
Net amount recognized in the Consolidated Balance Sheets:
Pension liability (b)			(25,681)	$ (28,850)	$ (27,141)	$ (27,730)	(27,641)	$ (32,887)	$ (32,967)	$ (28,540)
Minimum regulatory benefit for Philippine legal entity			500				500
Amounts recognized in accumulated other comprehensive loss, net of tax consist of:
Net actuarial loss	(8,059)	(9,301)
Net amount recognized in accumulated other comprehensive loss			8,059	$ 8,978	$ 9,269	$ 9,525	9,301	$ 10,691	$ 10,831	$ 11,457
Plans with underfunded or non-funded accumulated benefit obligation:
Aggregate fair value of plan assets	75,875	62,952	75,875				62,952
Overfunded Plan [Member]
Change in Plan Assets:
Fair value of plan assets at end of period	75,875
Plans with underfunded or non-funded accumulated benefit obligation:
Aggregate fair value of plan assets	75,875		75,875
Underfunded Plan [Member]
Change in Plan Assets:
Fair value of plan assets at beginning of period	62,952
Fair value of plan assets at end of period		62,952
Plans with underfunded or non-funded accumulated benefit obligation:
Aggregate fair value of plan assets	62,952	62,952					62,952
Underfunded Or Unfunded Plan [Member]
Change in Plan Assets:
Fair value of plan assets at beginning of period	62,883
Fair value of plan assets at end of period	75,875	62,883
Plans with underfunded or non-funded accumulated benefit obligation:
Aggregate projected benefit obligation			100,961				90,050
Aggregate accumulated benefit obligation			100,961				90,050
Aggregate fair value of plan assets	75,875	$ 62,883	75,875				62,883
U.K. And Asterion Plans
Net amount recognized in the Consolidated Balance Sheets:
Pension liability (b)			(25,681)				(27,641)
U.K. Pension Plan
Net amount recognized in the Consolidated Balance Sheets:
Pension liability (b)			(20,600)				(22,000)
Asterion Pension Plan
Net amount recognized in the Consolidated Balance Sheets:
Pension liability (b)			(2,400)				(2,800)
Norway Pension Plan
Net amount recognized in the Consolidated Balance Sheets:
Pension liability (b)			(100)				(500)
German Pension Plan
Net amount recognized in the Consolidated Balance Sheets:
Pension liability (b)			(2,100)				$ (1,800)
German Pension Plan | Unfunded Plan
Change in Plan Assets:
Fair value of plan assets at end of period	0
Plans with underfunded or non-funded accumulated benefit obligation:
Aggregate fair value of plan assets	$ 0		$ 0