Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash	$ 424,200	$ 367,200
Cash equivalents - money market funds	6,000	6,000
Restricted cash	1,406	1,428
Restricted cash, outstanding letter of credit	1,000	1,000
Restricted cash, guaranteed investment certificate for collateralizing an available credit facility	100	100
Restricted cash, foreign tender requirements	$ 300	$ 300