Fair Value of Financial Instruments - Swaps (Details) £ in Thousands, $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2011 contract	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2010 contract
Interest rate swaps
Derivative information
Number of derivative contracts entered into by the entity	3
Fixed interest rate (as a percent)	1.92%
Derivative term	4 years
Cross currency swaps
Derivative information
Number of derivative contracts entered into by the entity					3
Notional amount of each derivative contract		£ 194,200	$ 300,000
Forward rate (as a percent)		1.565	1.565
Cross currency swaps | Miscellaneous, net
Derivative information
Hedge ineffectiveness (gain) / loss | $			$ 751	$ 1,934