Fair Value of Financial Instruments Financial Instruments Carried at Fair Value(Details) £ in Thousands	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value		$ 1,530,000	$ 136,000
Fair Value, Inputs, Level 2 [Member] | Interest rate swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value, Interest rate swap agreements		0	136,000
Financial liabilities carried at fair value, Interest rate swap agreements		12,501,000	4,711,000
Fair Value, Inputs, Level 2 [Member] | British pound forward contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value, Interest rate swap agreements		1,530,000	$ 0
Fair Value, Inputs, Level 3 [Member] | Accrued deferred consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities carried at fair value, Accrued deferred consideration	£ 24,200	$ 35,680,000