Supplemental Cash Flow Information (Schedule of Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 254,103	$ 207,867	$ 166,501
Restricted cash, Current	113,391	50,222
Restricted cash, Non-current		500,000
Cash, cash equivalents, and restricted cash	$ 367,494	$ 758,089	$ 362,672	$ 293,246