Summary of Significant Accounting Policies Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and cash equivalents in balance sheet	$ 46,407	$ 12,620	$ 15,256	$ 28,947
Restricted cash, current portion in balance sheet	4,597	59	1,092	901
Restricted cash in other assets in balance sheet		342	342	683
Total cash, cash equivalents and restricted cash in statements of cash flows	51,004	13,021	16,690	30,531
Accounting Standards Update 2016-18
Total cash, cash equivalents and restricted cash in statements of cash flows		$ 401	$ 1,434	$ 1,584
Letter of Credit
Restricted cash, current portion in balance sheet	4,200
Deposit per credit card terms
Restricted cash, current portion in balance sheet	$ 300