Segments (Total Assets) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Assets	$ 224,303.8	$ 221,023.2
Parent | Retirement Solutions | Retirement
Segment Reporting Information [Line Items]
Assets	95,977.5	92,336.7
Parent | Retirement Solutions | Annuities
Segment Reporting Information [Line Items]
Assets	26,213.7	26,528.3
Parent | Investment Management
Segment Reporting Information [Line Items]
Assets	478.0	463.3
Parent | Insurance Solutions | Individual Life
Segment Reporting Information [Line Items]
Assets	26,626.7	25,592.2
Parent | Insurance Solutions | Employee Benefits
Segment Reporting Information [Line Items]
Assets	2,606.2	2,518.5
Parent | Total Ongoing Businesses
Segment Reporting Information [Line Items]
Assets	151,902.1	147,439.0
Parent | Corporate
Segment Reporting Information [Line Items]
Assets	4,057.5	4,802.8
Parent | Closed Blocks
Segment Reporting Information [Line Items]
Assets	58,259.0	60,460.1
Parent | Closed Blocks | Closed Block Variable Annuity
Segment Reporting Information [Line Items]
Assets	48,654.9	49,483.5
Parent | Closed Blocks | Closed Block Institutional Spread Products
Segment Reporting Information [Line Items]
Assets	2,089.4	3,390.1
Parent | Closed Blocks | Closed Block Other
Segment Reporting Information [Line Items]
Assets	7,514.7	7,586.5
Parent | Total Segment
Segment Reporting Information [Line Items]
Assets	214,218.6	212,701.9
Noncontrolling Interest
Segment Reporting Information [Line Items]
Assets	$ 10,085.2	$ 8,321.3