Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Stock-based compensation expense	$ 7.6	$ 4.7
Accrued liabilities	18.0	17.0
Deferred revenue	5.5	3.7
Net operating loss carryforwards - U.S.	0.2	0.2
Net operating loss carryforwards - Non-U.S.	4.5	2.4
Deferred royalty revenue	0.2	0.3
Allowance for doubtful accounts	1.4	1.4
Deferred rent	8.0	7.4
Unrealized exchange losses, net	0.0	0.2
Other	0.6	0.6
Total deferred tax assets	46.0	37.9
Deferred tax liabilities:
Acquired intangible assets	(82.7)	(16.5)
Property, equipment and capitalized software	(25.8)	(26.7)
Unrealized exchange gains, net	(1.1)	0.0
Prepaid expenses	(9.1)	(7.1)
Investments in unconsolidated entities	(6.3)	(4.8)
Withholding tax - foreign dividends	(3.0)	(3.0)
Total deferred tax liabilities	128.0	58.1
Net deferred tax liability before valuation allowance	82.0	20.2
Valuation allowance	(2.3)	(2.0)
Total deferred tax liabilities	$ (84.3)	$ (22.2)