Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Available-for-sale Debt Securities, Amortized Cost Basis	$ 8,477.3	$ 7,993.1
Available-for-sale Equity Securities, Amortized Cost Basis	$ 632.0	$ 452.1
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	75,000,000	75,000,000
Preferred Stock, Shares Outstanding	0	0
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Issued	260,462,217	259,490,089
Common Class B [Member]
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares Authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	0	0