Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Available for sale:
Fixed maturity securities (amortized costs)	$ 8,011.7	$ 8,149.4
Equity securities - cost	1,925.8	1,826.4
Held to maturity securities
Fixed maturity securities (fair value)	$ 652.8	$ 359.7
Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred Stock, authorized shares (in shares)	75,000,000	75,000,000
Preferred Stock, outstanding shares (in shares)	0	0
Common Stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common Stock, authorized shares (in shares)	500,000,000	500,000,000
Common Stock, issued shares (in shares)	262,445,592	261,968,328
Common Class B [Member]
Held to maturity securities
Common Stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common Stock, authorized shares (in shares)	100,000,000	100,000,000
Common Stock, issued shares (in shares)	0	0