13. Fair Value of Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
ASSETS:
U.S. government and agency	$ 932.7
State and political subdivision	344.5
Foreign government	214.6
Corporate	7,406.4
Commercial mortgage-backed ("CMBS")	973.3
Residential mortgage-backed ("RMBS")	1,881.6
CDO/CLO	216.5
Other asset-backed	467.1
Available-for-sale equity securities	30.9
Derivative assets	195.1
Fair value investments	213.8
Separate account assets	3,395.4	3,816.9
Total assets	16,271.9
LIABILITIES:
Derivative liabilities	60.0
Embedded derivatives	84.4
Total liabilities	144.4
As restated and amended [Member]
ASSETS:
U.S. government and agency		741.8
State and political subdivision		281.8
Foreign government		205.2
Corporate		6,558.2
Commercial mortgage-backed ("CMBS")		1,129.3
Residential mortgage-backed ("RMBS")		2,107.0
CDO/CLO		232.4
Other asset-backed		541.3
Available-for-sale equity securities		35.7
Derivative assets		162.2
Fair value investments		184.0
Separate account assets		3,816.9
Total assets		15,995.8
LIABILITIES:
Derivative liabilities		24.2
Embedded derivatives		84.5
Total liabilities		108.7
Level 1 [member]
ASSETS:
U.S. government and agency	499.7
State and political subdivision
Foreign government
Corporate
Commercial mortgage-backed ("CMBS")
Residential mortgage-backed ("RMBS")
CDO/CLO
Other asset-backed
Available-for-sale equity securities	1.6
Derivative assets	19.8
Fair value investments	31.8
Separate account assets	3,395.4
Total assets	3,948.3
LIABILITIES:
Derivative liabilities
Embedded derivatives
Total liabilities
Level 1 [member] | As restated and amended [Member]
ASSETS:
U.S. government and agency		268.2
State and political subdivision
Foreign government
Corporate
Commercial mortgage-backed ("CMBS")
Residential mortgage-backed ("RMBS")
CDO/CLO
Other asset-backed
Available-for-sale equity securities		1.5
Derivative assets		18.9
Fair value investments		23.7
Separate account assets		3,738.6
Total assets		4,050.9
LIABILITIES:
Derivative liabilities
Embedded derivatives
Total liabilities
Level 2 [Member]
ASSETS:
U.S. government and agency	112.4
State and political subdivision	151.6
Foreign government	159.6
Corporate	3,673.2
Commercial mortgage-backed ("CMBS")	899.6
Residential mortgage-backed ("RMBS")	1,048.8
CDO/CLO
Other asset-backed	146.1
Available-for-sale equity securities
Derivative assets	175.3
Fair value investments	17.9
Separate account assets
Total assets	6,384.5
LIABILITIES:
Derivative liabilities	60.0
Embedded derivatives
Total liabilities	60.0
Level 2 [Member] | As restated and amended [Member]
ASSETS:
U.S. government and agency		137.4
State and political subdivision		165.2
Foreign government		153.4
Corporate		3,056.7
Commercial mortgage-backed ("CMBS")		1,028.7
Residential mortgage-backed ("RMBS")		1,162.8
CDO/CLO
Other asset-backed		205.8
Available-for-sale equity securities		4.8
Derivative assets		143.3
Fair value investments		15.5
Separate account assets		78.3
Total assets		6,151.9
LIABILITIES:
Derivative liabilities		24.2
Embedded derivatives
Total liabilities		24.2
Level 3 [Member]
ASSETS:
U.S. government and agency	320.6
State and political subdivision	192.9
Foreign government	55.0
Corporate	3,733.2
Commercial mortgage-backed ("CMBS")	73.7
Residential mortgage-backed ("RMBS")	832.8
CDO/CLO	216.5
Other asset-backed	321.0
Available-for-sale equity securities	29.3
Derivative assets
Fair value investments	164.1
Separate account assets
Total assets	5,939.1
LIABILITIES:
Derivative liabilities
Embedded derivatives	84.4
Total liabilities	84.4
Level 3 [Member] | As restated and amended [Member]
ASSETS:
U.S. government and agency		336.2
State and political subdivision		116.6
Foreign government		51.8
Corporate		3,501.5
Commercial mortgage-backed ("CMBS")		100.6
Residential mortgage-backed ("RMBS")		944.2
CDO/CLO		232.4
Other asset-backed		335.5
Available-for-sale equity securities		29.4
Derivative assets
Fair value investments		144.8
Separate account assets
Total assets		5,793.0
LIABILITIES:
Derivative liabilities
Embedded derivatives		84.5
Total liabilities		$ 84.5