Investment Securities (Fair Value Measurement by Level) (Details) (USD $) In Millions, unless otherwise specified																																																																																																																																																																																																																																																																																																														3 Months Ended	12 Months Ended
	Dec. 31, 2012	Mar. 31, 2013 Fair Value		Dec. 31, 2012 Fair Value		Mar. 31, 2012 Fair Value		Dec. 31, 2011 Fair Value		Mar. 31, 2013 Level 1 Inputs		Dec. 31, 2012 Level 1 Inputs		Mar. 31, 2012 Level 1 Inputs		Dec. 31, 2011 Level 1 Inputs		Mar. 31, 2013 Level 2 Inputs	Dec. 31, 2012 Level 2 Inputs	Mar. 31, 2012 Level 2 Inputs	Dec. 31, 2011 Level 2 Inputs	Mar. 31, 2013 Debt securities issued by corporations		Dec. 31, 2012 Debt securities issued by corporations		Mar. 31, 2013 Mortgage-backed and asset-backed securities Fair Value	Dec. 31, 2012 Mortgage-backed and asset-backed securities Fair Value	Mar. 31, 2013 Mortgage-backed and asset-backed securities Level 2 Inputs	Dec. 31, 2012 Mortgage-backed and asset-backed securities Level 2 Inputs	Mar. 31, 2013 Mortgage-backed and asset-backed securities Level 3 Inputs	Dec. 31, 2012 Mortgage-backed and asset-backed securities Level 3 Inputs	Mar. 31, 2013 Fixed maturity investments. Level 3 Inputs	Dec. 31, 2012 Fixed maturity investments. Level 3 Inputs	Mar. 31, 2012 Fixed maturity investments. Level 3 Inputs	Dec. 31, 2011 Fixed maturity investments. Level 3 Inputs	Mar. 31, 2013 Common equity securities Level 3 Inputs	Dec. 31, 2012 Common equity securities Level 3 Inputs	Mar. 31, 2012 Common equity securities Level 3 Inputs	Dec. 31, 2011 Common equity securities Level 3 Inputs	Mar. 31, 2013 Convertible fixed maturity investments Level 3 Inputs	Dec. 31, 2012 Convertible fixed maturity investments Level 3 Inputs	Mar. 31, 2012 Convertible fixed maturity investments Level 3 Inputs	Dec. 31, 2011 Convertible fixed maturity investments Level 3 Inputs	Mar. 31, 2013 Other long-term investments Level 3 Inputs	Dec. 31, 2012 Other long-term investments Level 3 Inputs	Mar. 31, 2012 Other long-term investments Level 3 Inputs		Dec. 31, 2011 Other long-term investments Level 3 Inputs		Mar. 31, 2013 Fair value measured on a recurring basis Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis U.S. Government and agency obligations Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis U.S. Government and agency obligations Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis U.S. Government and agency obligations Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis U.S. Government and agency obligations Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis U.S. Government and agency obligations Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis U.S. Government and agency obligations Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis U.S. Government and agency obligations Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis U.S. Government and agency obligations Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Consumer Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Industrial Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Financials Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Financials Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Financials Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Financials Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Financials Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Financials Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Financials Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Financials Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Communications Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Communications Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Communications Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Communications Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Communications Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Communications Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Communications Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Communications Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Basic materials Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Energy Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Energy Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Energy Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Energy Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Energy Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Energy Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Energy Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Energy Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Utilities Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Technology Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Technology Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Technology Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Technology Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Technology Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Technology Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Technology Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Technology Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Other: Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Other: Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Other: Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Other: Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Other: Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Other: Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Debt securities issued by corporations Other: Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Debt securities issued by corporations Other: Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Municipal obligations Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Municipal obligations Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Municipal obligations Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Municipal obligations Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Municipal obligations Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Municipal obligations Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Municipal obligations Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Municipal obligations Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Mortgage-backed and asset-backed securities Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Foreign government, agency and provincial obligations Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Non-cumulative perpetual preference shares Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Fixed maturity investments. Fair Value		Dec. 31, 2012 Fair value measured on a recurring basis Fixed maturity investments. Fair Value		Mar. 31, 2013 Fair value measured on a recurring basis Fixed maturity investments. Level 1 Inputs		Dec. 31, 2012 Fair value measured on a recurring basis Fixed maturity investments. Level 1 Inputs		Mar. 31, 2013 Fair value measured on a recurring basis Fixed maturity investments. Level 2 Inputs		Dec. 31, 2012 Fair value measured on a recurring basis Fixed maturity investments. Level 2 Inputs		Mar. 31, 2013 Fair value measured on a recurring basis Fixed maturity investments. Level 3 Inputs		Dec. 31, 2012 Fair value measured on a recurring basis Fixed maturity investments. Level 3 Inputs		Mar. 31, 2013 Fair value measured on a recurring basis Short-term investments Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Short-term investments Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Short-term investments Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Short-term investments Level 1 Inputs	Mar. 31, 2012 Fair value measured on a recurring basis Short-term investments Level 1 Inputs	Dec. 31, 2011 Fair value measured on a recurring basis Short-term investments Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Short-term investments Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Short-term investments Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Short-term investments Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Short-term investments Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Consumer Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Consumer Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Consumer Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Consumer Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Consumer Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Consumer Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Consumer Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Consumer Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Financials Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Financials Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Financials Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Financials Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Financials Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Financials Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Financials Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Financials Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Communications Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Communications Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Communications Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Communications Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Communications Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Communications Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Communications Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Communications Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Basic materials Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Basic materials Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Basic materials Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Basic materials Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Basic materials Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Basic materials Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Basic materials Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Basic materials Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Energy Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Energy Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Energy Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Energy Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Energy Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Energy Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Energy Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Energy Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Utilities Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Utilities Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Utilities Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Utilities Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Utilities Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Utilities Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Utilities Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Utilities Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Technology Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Technology Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Technology Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Technology Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Technology Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Technology Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Technology Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Technology Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Other: Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Other: Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Other: Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Other: Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Other: Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Other: Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Other: Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Other: Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Common equity securities Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Common equity securities Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Convertible fixed maturity investments Fair Value	Dec. 31, 2012 Fair value measured on a recurring basis Convertible fixed maturity investments Fair Value	Mar. 31, 2013 Fair value measured on a recurring basis Convertible fixed maturity investments Level 1 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Convertible fixed maturity investments Level 1 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Convertible fixed maturity investments Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Convertible fixed maturity investments Level 2 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Convertible fixed maturity investments Level 3 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Convertible fixed maturity investments Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Other long-term investments Fair Value		Dec. 31, 2012 Fair value measured on a recurring basis Other long-term investments Fair Value		Mar. 31, 2013 Fair value measured on a recurring basis Other long-term investments Level 1 Inputs		Dec. 31, 2012 Fair value measured on a recurring basis Other long-term investments Level 1 Inputs		Mar. 31, 2013 Fair value measured on a recurring basis Other long-term investments Level 2 Inputs		Dec. 31, 2012 Fair value measured on a recurring basis Other long-term investments Level 2 Inputs		Mar. 31, 2013 Fair value measured on a recurring basis Other long-term investments Level 3 Inputs		Dec. 31, 2012 Fair value measured on a recurring basis Other long-term investments Level 3 Inputs		Mar. 31, 2012 Fair value measured on a recurring basis Other long-term investments Level 3 Inputs	Dec. 31, 2011 Fair value measured on a recurring basis Other long-term investments Level 3 Inputs	Mar. 31, 2013 Fair value measured on a recurring basis Forward Contracts Level 2 Inputs	Dec. 31, 2012 Fair value measured on a recurring basis Forward Contracts Level 2 Inputs	Mar. 31, 2013 Segment, Discontinued Operations	Dec. 31, 2012 Segment, Discontinued Operations	Mar. 31, 2012 Segment, Discontinued Operations
Investment securities
Fair value investments		$ 6,580.6	[1],[2]	$ 6,950.7	[1],[2]	$ 6,706.3	[3],[4]	$ 7,500.8	[3],[4]	$ 1,386.4	[5]	$ 1,355.1	[5]	$ 1,105.8	[6]	$ 1,033.1	[6]	$ 4,795.9	$ 5,206.1	$ 5,115.0	$ 6,088.2	$ 2,411.1	[7]	$ 2,385.1	[7]	$ 1,707.3	$ 2,095.6	$ 1,677.2	$ 2,073.5	$ 30.1	$ 22.1	$ 101.0	$ 92.9	$ 179.2	$ 78.9	$ 36.8	$ 37.3	$ 32.8	$ 32.3	$ 0	$ 0	$ 0	$ 0	$ 260.5	$ 259.3	$ 273.5	[3]	$ 268.3	[3],[4]	$ 7,235.0	$ 7,581.3	$ 2,040.8	$ 1,985.7	$ 4,795.9	$ 5,206.1	$ 398.3	$ 389.5	$ 435.5	$ 440.1	$ 364.6	$ 369.1	$ 70.9	$ 71.0	$ 0	$ 0	$ 2,409.7	$ 2,385.1	$ 0	$ 1.0	$ 2,409.7	$ 2,384.1	$ 0	$ 0	$ 735.5	$ 727.1	$ 0	$ 0	$ 735.5	$ 727.1	$ 0	$ 0	$ 308.0	$ 330.8	$ 0	$ 0	$ 308.0	$ 330.8	$ 0	$ 0	$ 378.4	$ 401.4	$ 0	$ 1.0	$ 378.4	$ 400.4	$ 0	$ 0	$ 331.6	$ 276.1	$ 0	$ 0	$ 331.6	$ 276.1	$ 0	$ 0	$ 211.6	$ 189.1	$ 0	$ 0	$ 211.6	$ 189.1	$ 0	$ 0	$ 183.2	$ 181.5	$ 0	$ 0	$ 183.2	$ 181.5	$ 0	$ 0	$ 202.3	$ 204.2	$ 0	$ 0	$ 202.3	$ 204.2	$ 0	$ 0	$ 53.0	$ 54.0	$ 0	$ 0	$ 53.0	$ 54.0	$ 0	$ 0	$ 6.1	$ 20.9	$ 0	$ 0	$ 6.1	$ 20.9	$ 0	$ 0	$ 5.2	$ 5.2	$ 0	$ 0	$ 5.2	$ 5.2	$ 0	$ 0	$ 1,707.3	$ 2,095.6	$ 0	$ 0	$ 1,677.2	$ 2,073.5	$ 30.1	$ 22.1	$ 506.1	$ 521.9	$ 48.5	$ 52.1	$ 457.6	$ 469.8	$ 0	$ 0	$ 87.5	$ 86.4	$ 0	$ 0	$ 16.6	$ 15.6	$ 70.9	$ 70.8	$ 5,151.3	[1]	$ 5,534.3	[8]	$ 413.1	[1]	$ 422.2	[8]	$ 4,637.2	[1]	$ 5,019.2	[8]	$ 101.0	[1]	$ 92.9	[8]	$ 654.4	$ 630.6	$ 654.4	$ 630.6			$ 0	$ 0	$ 0	$ 0	$ 305.8	$ 255.6	$ 305.8	$ 255.6	$ 0	$ 0	$ 0	$ 0	$ 320.1	$ 324.5	$ 283.3	$ 286.3	$ 0	$ 0.9	$ 36.8	$ 37.3	$ 39.9	$ 35.2	$ 39.9	$ 35.2	$ 0	$ 0	$ 0	$ 0	$ 77.6	$ 103.3	$ 77.6	$ 103.3	$ 0	$ 0	$ 0	$ 0	$ 86.2	$ 101.0	$ 86.2	$ 101.0	$ 0	$ 0	$ 0	$ 0	$ 39.7	$ 43.6	$ 39.6	$ 43.4	$ 0.1	$ 0.2	$ 0	$ 0	$ 76.9	$ 55.0	$ 76.9	$ 55.0	$ 0	$ 0	$ 0	$ 0	$ 127.0	$ 111.5	$ 64.0	$ 53.1	$ 63.0	$ 58.4	$ 0	$ 0	$ 1,073.2	$ 1,029.7	$ 973.3	$ 932.9	$ 63.1	$ 59.5	$ 36.8	$ 37.3	$ 95.6	$ 127.4	$ 0	$ 0	$ 95.6	$ 127.4	$ 0	$ 0	$ 260.5	[2]	$ 259.3	[9]	$ 0	[2]	$ 0	[9]	$ 0	[2]	$ 0	[9]	$ 260.5	[2]	$ 259.3	[9]
Carrying value of investment accounted for using the equity method																																																																																																																																																																																																				654.4	630.6	877.5	846.0																																																																																																	34.9		35.0		33.0	33.2
Realized and unrealized (losses) gains																																																																																																																																																																																																																																																																																																														(0.2)	(0.1)
Fixed maturity investments reclassified to assets held for sale	$ (338.1)																																																																																																																																																																																																																																																																																																															$ (296.9)	$ (338.1)	$ (111.8)

[1] Carrying value includes $296.9 that is classified as assets held for sale relating to discontinued operations.

[2] Excludes carrying value of $34.9 associated with other long-term investment limited partnerships accounted for using the equity method and $(0.2) related to forward contracts.

[3] Excludes carrying value of $33.0 and $33.2 at March 31, 2012 and January 1, 2012 associated with other long-term investment limited partnerships accounted for using the equity method.

[4] Carrying value includes $111.8 that is classified as assets held for sale relating to discontinued operations.

[5] Excludes carrying value of $630.6 and $654.4 at January 1, 2013 and March 31, 2013 and realized and unrealized gain for the period of $0.1 associated with short-term investments classified as level 1.

[6] Excludes carrying value of $877.5 and $846.0 at March 31, 2012 and January 1, 2012 and realized and unrealized loss for the period of $0.3 associated with short-term investments classified as level 1.

[7] Credit ratings are assigned based on the following hierarchy: 1) Standard and Poor's Financial Services LLC ("Standard & Poor’s") and 2) Moody’s Investor Service ("Moody's").

[8] Carrying value includes $338.1 that is classified as assets held for sale relating to discontinued operations.

[9] Excludes carrying value of $35.0 associated with other long-term investment limited partnerships accounted for using the equity method and $(0.1) related to currency forward contracts.