Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total Property and Equipment, Gross	$ 119,051		$ 155,562
Less: Accumulated depreciation	(81,827)		(72,629)
Property and Equipment, Net	37,224	$ 36,837	82,933
Computer equipment
Property, Plant and Equipment [Line Items]
Total Property and Equipment, Gross	14,249		12,258
Software, including internal-use software
Property, Plant and Equipment [Line Items]
Total Property and Equipment, Gross	89,072		82,426
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Total Property and Equipment, Gross	7,288		7,315
Buildings
Property, Plant and Equipment [Line Items]
Total Property and Equipment, Gross	1,666		49,169
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total Property and Equipment, Gross	$ 6,776		$ 4,394