Schedule of Tangible Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets
Long-lived Assets	$ 696,567	$ 629,987	$ 546,651
United States
Revenues from External Customers and Long-Lived Assets
Long-lived Assets	493,300	469,450
United Kingdom
Revenues from External Customers and Long-Lived Assets
Long-lived Assets	138,546	92,813
Other countries
Revenues from External Customers and Long-Lived Assets
Long-lived Assets	$ 64,721	$ 67,724