Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 236,412	$ 388,490	$ 249,871
Restricted cash	188,938	201,300	173,855
Total Cash and cash equivalents and Restricted cash shown in the Consolidated Statements of Cash Flows	$ 425,350	$ 589,790	$ 423,726	$ 532,782