Supplemental Cash Flow Information (Schedule of Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 236,894	$ 207,867	$ 294,074
Restricted cash, Current	137,986	50,222
Restricted cash, Non-current	500,000	500,000
Cash, cash equivalents, and restricted cash	$ 874,880	$ 758,089	$ 412,018	$ 293,246