Summary of Significant Accounting Policies and Practices Goodwill and aquired intangible asset impairment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Restricted cash	$ 76,595	$ 81,374
Impairment of Intangible Assets, Finite-lived	$ 7,049	$ 2,286