Net Periodic Cost for U.K Plan and Japan Plan (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
UNITED KINGDOM
Components of the net periodic pension cost:
Service cost	$ 0	$ 0
Interest cost	1,589	1,403	1,359
Expected return on plan assets	(1,958)	(1,595)	(1,270)
Amortization of actuarial losses	374	668	392
Net periodic pension cost	5	476	481
JAPAN
Components of the net periodic pension cost:
Service cost	101	99	121
Interest cost	13	10	15
Expected return on plan assets	(6)	(7)
Amortization of the unrecognized transition obligation	29	14	37
Amortization of prior service cost	18	12	3
Other	18
Net periodic pension cost	$ 173	$ 128	$ 176