Financing Agreements - Long-term Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$ 3,515.0	$ 3,514.7
Less: Current portion of long-term debt	0	0
Long-term debt	3,515.0	3,514.7
Debentures | 7.25% Lion Connecticut Holdings Inc. debentures, due 2023
Debt Instrument [Line Items]
Long-term debt	158.7	158.6
Annual interest rate on loan	7.25%
Debentures | 7.63% Lion Connecticut Holdings Inc. debentures, due 2026
Debt Instrument [Line Items]
Long-term debt	232.2	232.1
Annual interest rate on loan	7.63%
Debentures | 6.97% Lion Connecticut Holdings Inc. debentures, due 2036
Debt Instrument [Line Items]
Long-term debt	108.6	108.6
Annual interest rate on loan	6.97%
Notes Payable | 8.42% Equitable of Iowa Companies Capital Trust II Notes, due 2027
Debt Instrument [Line Items]
Long-term debt	13.8	13.8
Annual interest rate on loan	8.42%
Property Loan | 1.00% Windsor Property Loan
Debt Instrument [Line Items]
Long-term debt	4.9	4.9
Annual interest rate on loan	1.00%
Senior Notes | 5.5% Senior Notes, due 2022
Debt Instrument [Line Items]
Long-term debt	849.6	849.6
Annual interest rate on loan	5.50%
Senior Notes | 2.9% Senior Notes, due 2018
Debt Instrument [Line Items]
Long-term debt	998.6	998.5
Annual interest rate on loan	2.90%
Senior Notes | 5.65% Fixed-to-Floating Rate Junior Subordinated Notes, due 2053
Debt Instrument [Line Items]
Annual interest rate on loan	5.65%
Senior Notes | 5.7% Senior Notes, due 2043
Debt Instrument [Line Items]
Long-term debt	398.6	398.6
Annual interest rate on loan	5.70%
Junior Subordinated Notes (2053 Notes) | 5.65% Fixed-to-Floating Rate Junior Subordinated Notes, due 2053
Debt Instrument [Line Items]
Long-term debt	$ 750.0	$ 750.0