CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Change in Net Unrealized Gains and Losses on Securities Not Other-Than-Temporarily Impaired, tax expense	$ 470.9	$ 812.4	$ 522.6
Change in Net Unrealized Gains and Losses on Securities Other-Than-Temporary Impaired Tax Benefit	0	1.1	0.5
Total Change in Net Unrealized Gains and Losses on Securities Before Reclassification Tax Expense	470.9	811.3	522.1
Reclassification Adjustment for Net Realized Investment (Gain) Loss, tax expense	3.2	13.0	3.5
Change in Gain on Cash Flow Hedges Tax Expense	(4.3)	25.2	(5.0)
Change in Adjustment to Reserves for Future Policy and Contract Benefits Net of Reinsurance and Other tax expense benefit	325.6	701.5	499.6
Change in Foreign Currency Translation Adjustment Tax Expense	0	0	0.6
Change in Unrecognized Pension and Postretirement Benefit Cost Tax Expense	$ 68.0	$ 67.4	$ 12.7