Summary of Significant Accounting Policies Revenue Recognition (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Development service fee expense		$ 85,805	$ 12,165	$ 0
Previously Reported [Member] | Other Income [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Development service fee income	$ 3,789			6,159
Previously Reported [Member] | General and Administrative Expense [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Development service fee expense	$ 3,210			$ 3,730