Schedule II - Condensed Financial Information of Registrant Balance Sheets (details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Assets:
Bonds and Notes	$ 551.2
Short-term investments	1,124.8	1,264.9
Other assets	455.7	454.2
Total Assets	16,534.4	16,226.8
Liabilities:
Debt	569.2	572.9
Commitments and contingent liabilities
Total Liabilities	12,759.4	12,630.6
Common Shareholders' Equity:
Common stock		259.4	[1]
Additional paid-in capital		660.9
Retained earnings		2,222.3
Accumulated other comprehensive income (loss)		481.7
Unallocated ESSOP shares (at cost)		(28.2)
Total Common Shareholders' Equity	3,775.0	3,596.2
Liabilities and Common Shareholders' Equity:
Total Liabilities, Preferred Stock and Common Shareholders' Equity	16,534.4	16,226.8
Parent Company [Member]
Assets:
Bonds and Notes	10.5	55.8
Short-term investments	138.0	159.4
Cash	20.1	0
Investments in, and indebtedness of related parties	4,308.5	4,121.5
Other assets	87.4	114.2
Total Assets	4,564.6	4,451.1
Liabilities:
Accounts payable and accrued expenses	131.6	187.2
Debt	568.0	570.8
Indebtedness to affiliates and subsidiaries	89.8	96.8
Commitments and contingent liabilities
Total Liabilities	789.6	854.9
Common Shareholders' Equity:
Common stock	260.4	259.4
Additional paid-in capital	673.9	660.9
Retained earnings	2,485.3	2,222.3
Accumulated other comprehensive income (loss)	378.2	481.7
Unallocated ESSOP shares (at cost)	(23.0)	(28.2)
Total Common Shareholders' Equity	3,775.0	3,596.2
Liabilities and Common Shareholders' Equity:
Total Liabilities, Preferred Stock and Common Shareholders' Equity	$ 4,564.6	$ 4,451.1

[1] At December 31, 2013 and 2012, there were 75,000,000 shares of $0.01 par value preferred stock authorized, of which no shares were outstanding. As of the same dates, there were 500,000,000 shares of common stock, $1.00 par value, authorized, of which 260,462,217 and 259,490,089 were issued as of December 31, 2013 and 2012, respectively. At December 31, 2013 and 2012, there were 100,000,000 shares of Class B Common Stock, $1.00 par value, authorized, of which no shares were issued.