CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Change in Net Unrealized Gains and Losses on Securities Not Other-Than-Temporarily Impaired, tax expense	$ 812.4	$ 522.6	$ 1,375.9
Change in Net Unrealized Gains and Losses on Securities Other-Than-Temporarily Impaired, tax expense (benefit)	(1.1)	(0.5)	9.3
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	811.3	522.1	1,385.2
Reclassification Adjustment for Net Realized Investment (Gain) Loss, tax expense	13.0	3.5	(79.0)
Change in Net Gain on Cash Flow Hedges, tax expens (benefit)	25.2	(5.0)	(45.3)
Change in Adjustment to Reserves for Future Policy and Contract Benefits Net of Reinsurance and Other tax expense benefit	(703.3)	(501.0)	(816.6)
Change in Foreign Currency Translation Adjustment	0	0.6	0
Change in Unrecognized Pension and Postretirement Benefit Costs	$ (67.4)	$ (12.7)	$ 42.0