Deferred Contract Costs - Summary of Deferred Contract Costs (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Capitalized Contract Cost [Line Items]
Total deferred contract costs	$ 24.1	$ 20.2
Prepaid expenses and other current assets
Capitalized Contract Cost [Line Items]
Total deferred contract costs	3.7	2.8
Other assets
Capitalized Contract Cost [Line Items]
Total deferred contract costs	$ 20.4	$ 17.4