Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data	Sep. 30, 2011	Dec. 31, 2010
Condensed Consolidated Balance Sheets
Fixed maturities, available-for-sale, amortized cost (in dollars)	$ 15,817.3	$ 15,104.5
Equity securities, available-for-sale, cost (in dollars)	165.1	179.6
Securities pledged, amortized cost (in dollars)	$ 304.4	$ 936.5
Common stock, shares authorized	100,000	100,000
Common stock, shares issued	55,000	55,000
Common stock, shares outstanding	55,000	55,000
Common stock, per share value (in dollars per share)	$ 50	$ 50