Commitments and Contingent Liabilities Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liability	$ (233.6)
Retained earnings	$ 4,220.8		$ 3,849.8
Weighted average discount rate	5.66%
Weighted average remaining lease term	8 years 1 month
Lease cost	$ 18.8
Lease payments	$ 15.8
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use asset		$ 226.9
Lease liability		241.4
Retained earnings		$ 18.4