Summary of Significant Accounting Policies - ASC 606 - Cumulative Effect - Accumulated Deficit (Details) $ in Millions	Oct. 01, 2018 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Registration fees benefit period	24 months
Customer life period	60 months
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect adjustment, increase to the opening accumulated deficit	$ 0.9
Cumulative effect adjustment, increase to the opening accumulated deficit, tax	0.4
Cumulative effect on accumulated deficit, net of tax, effect of acceleration of revenue	0.9
Cumulative effect on accumulated deficit, net of tax, effect of deferral of registration fee	3.1
Cumulative effect on accumulated deficit, net of tax, effect of deferral of commission expense	1.5
Cumulative effect on accumulated deficit, net of tax, effect of additional performance obligation	0.2
Accounting Standards Update 2014-09 | Discontinued Operations, Held-for-sale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect on accumulated deficit, net of tax, effect of additional performance obligation	$ 0.2