Summary of Significant Accounting Policies, Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements
Operating lease right-of-use assets (included in other long-term assets)	$ 196.7
Lease liabilities	199.4
Retained earnings	$ 3,348.4		$ 3,028.7
Lease, practical expedient	true
Right-of-use assets obtained in exchange for lease liabilities	$ 98.6
Impact of ASU 2016-02
New Accounting Pronouncements
Operating lease right-of-use assets (included in other long-term assets)		$ 180.0
Lease liabilities		180.0
Retained earnings		$ 0.0