Long-term Debt Amortization of Term Loans (Details) - 12 months ended Dec. 31, 2016 - Credit Agreement [Member] £ in Thousands, $ in Thousands	GBP (£)	USD ($)	USD ($)
United States Term Loan [Member]
Debt Instrument, Prepayment, Principal		$ 317,100
Debt Instrument, Periodic Payment, Principal		26,900
British pound term loan [Member]
Debt Instrument, Prepayment, Principal	£ 700	900
Debt Instrument, Periodic Payment, Principal	2,500	3,200
March 31, 2017 through June 30, 2018 [Member] | United States Term Loan [Member]
Debt Instrument, Periodic Payment, Principal		5,083
March 31, 2017 through June 30, 2018 [Member] | British pound term loan [Member]
Debt Instrument, Periodic Payment, Principal | £	1,271
September 30, 2018 through December 31, 2019 [Member] | United States Term Loan [Member]
Debt Instrument, Periodic Payment, Principal		$ 10,167
September 30, 2018 through December 31, 2019 [Member] | British pound term loan [Member]
Debt Instrument, Periodic Payment, Principal | £	2,542
Maturity date - March 31, 2020 [Member] | United States Term Loan [Member]
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid			$ 1,336,500
Maturity date - March 31, 2020 [Member] | British pound term loan [Member]
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid | £	£ 75,532