Segments (Total Assets) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Assets	$ 223,510.7	$ 221,023.2
Parent | Retirement Solutions | Retirement
Segment Reporting Information [Line Items]
Assets	94,654.8	92,336.7
Parent | Retirement Solutions | Annuities
Segment Reporting Information [Line Items]
Assets	26,748.3	26,528.3
Parent | Investment Management
Segment Reporting Information [Line Items]
Assets	391.9	463.3
Parent | Insurance Solutions | Individual Life
Segment Reporting Information [Line Items]
Assets	25,920.8	25,592.2
Parent | Insurance Solutions | Employee Benefits
Segment Reporting Information [Line Items]
Assets	2,559.7	2,518.5
Parent | Total Ongoing Businesses
Segment Reporting Information [Line Items]
Assets	150,275.5	147,439.0
Parent | Corporate
Segment Reporting Information [Line Items]
Assets	4,566.8	4,802.8
Parent | Closed Blocks
Segment Reporting Information [Line Items]
Assets	59,797.4	60,460.1
Parent | Closed Blocks | Closed Block Variable Annuity
Segment Reporting Information [Line Items]
Assets	49,451.6	49,483.5
Parent | Closed Blocks | Closed Block Institutional Spread Products
Segment Reporting Information [Line Items]
Assets	2,711.3	3,390.1
Parent | Closed Blocks | Closed Block Other
Segment Reporting Information [Line Items]
Assets	7,634.5	7,586.5
Parent | Total Segment
Segment Reporting Information [Line Items]
Assets	214,639.7	212,701.9
Noncontrolling Interest
Segment Reporting Information [Line Items]
Assets	$ 8,871.0	$ 8,321.3