Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Restructuring (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 783,000	$ 0	$ 10,149,000	$ 0	$ 0
Restructuring cost expected to be incurred	$ 900,000		900,000
Office lease terminations and modifications [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			9,000,000.0
Transition services including severance costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			1,600,000
Operating lease adjustment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ (500,000)