10. Fair Value of Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
ASSETS:
U.S. government and agency	$ 285.1	$ 174.1
State and political subdivision	130.9	83.5
Foreign government	51.8	31.9
Corporate	1,897.5	1,204.7
CMBS	254.0	281.5
RMBS	422.5	531.5
CDO/CLO	56.8	62.5
Other asset-backed	118.6	142.4
Derivative assets	149.4	103.8
Inter-company reinsurance derivative asset		3.5
Fair value option investments	38.5	41.8
Separate account assets	2,061.8	2,546.8
Total assets	5,466.9	5,208.0
LIABILITIES:
Derivative liabilities	45.7	22.5
Embedded derivatives	79.5	82.3
Total liabilities	125.2	104.8
As restated and amended [Member]
ASSETS:
Separate account assets		2,546.8
Level 1 [member]
ASSETS:
U.S. government and agency	244.9
State and political subdivision
Foreign government
Corporate
CMBS
RMBS
CDO/CLO
Other asset-backed
Derivative assets	13.8
Inter-company reinsurance derivative asset
Fair value option investments
Separate account assets	2,061.8
Total assets	2,320.5
LIABILITIES:
Derivative liabilities
Embedded derivatives
Total liabilities
Level 1 [member] | As restated and amended [Member]
ASSETS:
U.S. government and agency		96.0
State and political subdivision
Foreign government
Corporate
CMBS
RMBS
CDO/CLO
Other asset-backed
Derivative assets		16.2
Inter-company reinsurance derivative asset
Fair value option investments
Separate account assets		2,546.8
Total assets		2,659.0
LIABILITIES:
Derivative liabilities
Embedded derivatives
Total liabilities
Level 2 [Member]
ASSETS:
U.S. government and agency	14.3
State and political subdivision	14.8
Foreign government	43.8
Corporate	1,096.0
CMBS	234.7
RMBS	199.9
CDO/CLO
Other asset-backed	38.5
Derivative assets	135.6
Inter-company reinsurance derivative asset
Fair value option investments	15.8
Separate account assets
Total assets	1,793.4
LIABILITIES:
Derivative liabilities	45.7
Embedded derivatives
Total liabilities	45.7
Level 2 [Member] | As restated and amended [Member]
ASSETS:
U.S. government and agency		46.4
State and political subdivision		34.8
Foreign government		28.8
Corporate		690.9
CMBS		246.1
RMBS		263.5
CDO/CLO
Other asset-backed		61.2
Derivative assets		87.6
Inter-company reinsurance derivative asset
Fair value option investments		14.3
Separate account assets
Total assets		1,473.6
LIABILITIES:
Derivative liabilities		22.5
Embedded derivatives
Total liabilities		22.5
Level 3 [Member]
ASSETS:
U.S. government and agency	25.9
State and political subdivision	116.1
Foreign government	8.0
Corporate	801.5
CMBS	19.3
RMBS	222.6
CDO/CLO	56.8
Other asset-backed	80.1
Derivative assets
Inter-company reinsurance derivative asset
Fair value option investments	22.7
Separate account assets
Total assets	1,353.0
LIABILITIES:
Derivative liabilities
Embedded derivatives	79.5
Total liabilities	79.5
Level 3 [Member] | As restated and amended [Member]
ASSETS:
U.S. government and agency		31.7
State and political subdivision		48.7
Foreign government		3.1
Corporate		513.8
CMBS		35.4
RMBS		268.0
CDO/CLO		62.5
Other asset-backed		81.2
Derivative assets
Inter-company reinsurance derivative asset		3.5
Fair value option investments		27.5
Separate account assets
Total assets		1,075.4
LIABILITIES:
Derivative liabilities
Embedded derivatives		82.3
Total liabilities		$ 82.3