Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 600,356	$ 373,173	$ 508,808	$ 370,741
Cash	544,300	367,200
Cash equivalents - money market funds	56,100	6,000
Restricted cash	5,050	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
Restricted cash, collateral requirement for VAT	$ 3,700