Summary of Significant Accounting Policies Supplemental Cash Flow Disclosure (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 194,654	$ 198,850
Current restricted cash	3,890	7,007
Restricted Cash and Cash Equivalents, Noncurrent	1,749	1,727
Restricted Cash and Cash Equivalents	5,639	8,734
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 200,293	$ 207,584	$ 165,938	$ 340,601