Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 279,980	$ 521,195
Restricted cash
Restricted cash	18,277	35,720
Restricted cash deposits kept as collateral for outstanding letters of credit	17,700	33,800
RMC
Restricted cash
Restricted cash	$ 602	$ 1,900