Segments (Operating Revenues) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Total operating revenues	$ 2,191.9	$ 2,178.9	$ 6,564.2	$ 6,366.9
Closed Block Variable Annuity	660.6	(66.1)	1,057.3	(570.4)
Net realized investment gains (losses) and related charges and adjustments	48.2	39.8	164.8	28.3
Gain (loss) on change in fair value of derivatives related to guaranteed benefits	48.2	35.1	0	125.8
Revenues related to businesses exited through reinsurance or divestment	(4.8)	(2.9)	81.1	(70.8)
Revenues attributable to noncontrolling interest	174.9	152.9	454.8	254.1
Other adjustments to operating revenues	72.1	97.6	237.9	260.6
Total revenues	3,191.1	2,435.3	8,560.1	6,394.5
Intersegment
Segment Reporting Information [Line Items]
Total operating revenues	40.0	38.6	118.3	117.8
Retirement Solutions | Retirement
Segment Reporting Information [Line Items]
Total operating revenues	605.7	606.9	1,797.1	1,787.0
Retirement Solutions | Annuities
Segment Reporting Information [Line Items]
Total operating revenues	344.6	319.1	1,029.8	930.7
Investment Management
Segment Reporting Information [Line Items]
Total operating revenues	168.3	160.1	492.0	440.6
Insurance Solutions | Individual Life
Segment Reporting Information [Line Items]
Total operating revenues	679.1	717.1	2,071.2	2,099.0
Insurance Solutions | Employee Benefits
Segment Reporting Information [Line Items]
Total operating revenues	345.9	316.2	1,027.3	946.0
Total Ongoing Businesses
Segment Reporting Information [Line Items]
Total operating revenues	2,143.6	2,119.4	6,417.4	6,203.3
Corporate
Segment Reporting Information [Line Items]
Total operating revenues	22.9	28.8	71.8	53.8
Closed Blocks
Segment Reporting Information [Line Items]
Total operating revenues	25.4	30.7	75.0	109.8
Closed Blocks | Closed Block Institutional Spread Products
Segment Reporting Information [Line Items]
Total operating revenues	18.6	23.1	53.2	87.7
Closed Blocks | Closed Block Other
Segment Reporting Information [Line Items]
Total operating revenues	$ 6.8	$ 7.6	$ 21.8	$ 22.1