Commitments and Contingencies - Employee Benefit Plans (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Employer matching contribution, percent of match	50.00%
Employer matching contribution percent of eligible compensation	5.00%
Employer contribution limit	$ 6,000
Employer contribution vesting period	5 years
Employer matching contributions		$ 3,200,000	$ 1,600,000	$ 1,400,000
Match Step One
Other Commitments [Line Items]
Employer matching contribution, percent of match		100.00%
Employer matching contribution percent of eligible compensation		3.00%
Match Step Two
Other Commitments [Line Items]
Employer matching contribution, percent of match		50.00%
Employer matching contribution percent of eligible compensation		2.00%