Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Restructuring (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 290,000	$ 0	$ 9,366,000	$ 0	$ 0
Restructuring cost expected to be incurred	$ 1,600,000		1,600,000
Office lease terminations and modifications [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			8,400,000
Transition services including severance costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			1,300,000
Operating lease adjustment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 300,000