Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Equity compensation plans	$ 18.7	$ 29.2
Payroll and benefits	8.0	22.7
Deferred interest	6.8	13.9
Net operating loss and credit carryforwards, net	28.1	12.7
Rent	7.4	11.0
Accounts receivable	5.4	8.3
Other	8.0	6.2
Trade credits	1.5	0.6
Total deferred tax assets	83.9	104.6
Deferred tax liabilities:
Software and intangibles	194.5	337.4
Deferred income	18.6	58.3
International investments	19.2	31.3
Property and equipment	20.4	30.3
Other	12.0	15.3
Total deferred tax liabilities	264.7	472.6
Deferred tax asset valuation allowance	15.5	1.2
Net deferred tax liabilities	$ 196.3	$ 369.2