Retirement Plans - UK plans (Details) - UK Plans $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) employee	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets	2.77%	3.48%
Fair value of plan assets	$ 38,520	$ 42,716
Funding deficit based on most recent valuation	$ 2,316	4,650	$ 1,000
Period over which the deficit is being funded	4 years
Transferred to defined contribution plan
Defined Benefit Plan Disclosure [Line Items]
Number of members in the plan | employee	6
Accrued pension liability	$ 4,100	$ 4,800
Still employed by company
Defined Benefit Plan Disclosure [Line Items]
Number of members in the plan | employee	3
Equities
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets	5.70%	6.20%
Fair value of plan assets	$ 9,122	$ 7,893
Gilts
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets	2.40%	2.40%
Fair value of plan assets	$ 15,459	$ 17,856
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets	3.30%	3.40%
Fair value of plan assets	$ 13,850	$ 16,915
Other (cash)
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets	0.50%	1.80%
Fair value of plan assets	$ 89	$ 52