Summary of Significant Accounting Policies New Accounting Standards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016		Mar. 31, 2018	[2]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			$ 0.2	[1]	$ 2.2
Net cash provided by operating activities	$ 364.1	$ 296.4	190.3
Net Cash Provided by (Used in) Financing Activities	93.4	587.3	(25.0)
Effect of exchange rate changes on cash and cash equivalents	(32.2)	(0.9)	(15.7)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			0.2	[1]	$ 3.3
Accounting Standards Update 2014-09 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle		1.5
Accounting Standards Update 2016-01 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle		1.1
Accounting Standards Update 2016-16 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle		0.7
Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities		44.3	22.8
Net Cash Provided by (Used in) Financing Activities		1.5	19.9
Effect of exchange rate changes on cash and cash equivalents		$ 11.3	3.6
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			$ 0.2
Minimum | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease Right-of-Use Asset	0.0
Lease Liability	260.0
Maximum | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease Right-of-Use Asset	0.0
Lease Liability	$ 360.0

[1] We elected to early adopt the provisions of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, in the fourth quarter of 2016 resulting in a cumulative effect adjustment to Retained Earnings for previously unrecognized excess tax benefits. See Note 1 for further discussion of the impacts of this standard.

[2] Effective January 1, 2018, we adopted the provisions of ASU 2014-09, Revenue From Contracts with Customers, ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, and ASU 2016-16, Intra-Entity Transfers of Assets Other Than Inventory. We recognized a cumulative effect adjustment to January 1, 2018 retained earnings as a result of adopting each of these standards. See Note 1 for further details of the impact of each standard.