12. Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Interest rate swaps [Member]
Derivative Instruments Maturity Period	2016-2027	2017-2026
Fair Value Notional Amount	$ 180.0	$ 131.0
Fair Value Assets	16.8
Fair Value Liabilities	8.2
Variance Swaps [member]
Derivative Instruments Maturity Period	2015-2017	2015-2017
Fair Value Notional Amount	0.9	0.9
Fair Value Assets
Fair Value Liabilities	3.1
Swaptions
Derivative Instruments Maturity Period	2024	2024
Fair Value Notional Amount	25.0	25.0
Fair Value Assets
Fair Value Liabilities
Swaptions | As restated and amended [Member]
Fair Value Assets		0.2
Fair Value Liabilities
Put options [Member]
Derivative Instruments Maturity Period	2015-2022	2015-2022
Fair Value Notional Amount	406.0	406.0
Fair Value Assets	80.9
Fair Value Liabilities
Call options [Member]
Derivative Instruments Maturity Period	2013-2017	2012-2016
Fair Value Notional Amount	1,261.7	700.4
Fair Value Assets	77.4
Fair Value Liabilities	48.7
Cross currency swaps [Member]
Derivative Instruments Maturity Period	2016	2012-2016
Fair Value Notional Amount	10.0	15.0
Fair Value Assets	0.2
Fair Value Liabilities
Equity futures [Member]
Derivative Instruments Maturity Period	2013	2012
Fair Value Notional Amount	184.2	70.0
Fair Value Assets	19.8
Fair Value Liabilities
Equity futures [Member] | As restated and amended [Member]
Fair Value Assets		18.5
Fair Value Liabilities
Total derivative instruments
Fair Value Notional Amount	2,067.8	1,348.3
Fair Value Assets	195.1
Fair Value Liabilities	60.0
Total derivative instruments | As restated and amended [Member]
Fair Value Assets		162.2
Fair Value Liabilities		24.2
Interest rate swaps | As restated and amended [Member]
Fair Value Assets		13.7
Fair Value Liabilities		5.2
Variance Swaps | As restated and amended [Member]
Fair Value Assets		2.8
Fair Value Liabilities
Put options | As restated and amended [Member]
Fair Value Assets		95.4
Fair Value Liabilities
Call options | As restated and amended [Member]
Fair Value Assets		31.4
Fair Value Liabilities		19.0
Cross currency swaps | As restated and amended [Member]
Fair Value Assets		0.2
Fair Value Liabilities