Summary of Significant Accounting Policies Restricted Cash (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of Significant Accounting Policies
Settlement agreement installment paid	$ 1,400
Restriction on cash deposits released	$ 4,200
Cash and cash equivalents in balance sheet		$ 61,926	$ 46,407
Restricted cash, current portion in balance sheet		55	4,597
Restricted cash in other assets in balance sheet		0
Total cash, cash equivalents and restricted cash in statements of cash flows		$ 61,981	$ 51,004	$ 13,021	$ 16,690