Investments Equity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Equity securities - cost	$ 2,396.6	$ 1,826.4
Available-for-sale Securities, Equity Securities	2,787.4	1,987.8
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity securities - cost	2,396.6	1,826.4
Equity securities, gross unrealized gains	423.1	266.7
Equity securities, gross unrealized losses	32.3	105.3
Available-for-sale Securities, Equity Securities	$ 2,787.4	$ 1,987.8