Income Taxes - Temporary Differences (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Operating Loss Carryforwards [Line Items]
Insurance reserves	$ 255.4	$ 269.6
Investments	87.5	89.2
Postemployment benefits	50.6	97.1
Compensation and benefits	44.4	22.9
Other assets	24.5	22.5
Total gross assets before valuation allowance	462.4	501.3
Less: Valuation allowance	11.1	11.1
Assets, net of valuation allowance	451.3	490.2
Net unrealized investment gains (losses)	(482.4)	(357.5)
Deferred policy acquisition costs	(143.8)	(127.0)
Value of business acquired	(332.2)	(360.9)
Total gross liabilities	(958.4)	(845.4)
Net deferred income tax liability	(507.1)	(355.2)
Current income tax payable to Parent	32.1	1.3
Operating loss carryforward | Foreign tax credits
Operating Loss Carryforwards [Line Items]
Tax valuation allowance	11.1	11.1
Operating loss carryforward | Net income (loss)
Operating Loss Carryforwards [Line Items]
Tax valuation allowance	62.8	62.8
Operating loss carryforward | Other comprehensive income (loss)
Operating Loss Carryforwards [Line Items]
Tax valuation allowance	(51.7)	(51.7)
ING U.S. Inc.
Operating Loss Carryforwards [Line Items]
Current income tax payable to Parent	$ 32.1	$ 1.3