Catastrophe Reinsurance - Coverage for Catastrophe Reinsurance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property and Casualty Insurance [Member] | Retained [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage	0.00%	0.00%	0.00%
Property and Casualty Insurance [Member] | First Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Percentage	95.00%	65.00%	65.00%
Property and Casualty Insurance [Member] | Second Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Percentage	95.00%	95.00%	95.00%
Property and Casualty Insurance [Member] | Third Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Percentage	95.00%	90.00%	90.00%
Property and Casualty Insurance [Member] | Fourth Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Percentage		50.00%	50.00%
Property and Casualty Insurance [Member] | Minimum [Member] | Retained [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Amount Retained	0	0	0
Property and Casualty Insurance [Member] | Minimum [Member] | First Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	50.0	50.0	50.0
Property and Casualty Insurance [Member] | Minimum [Member] | Second Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	100.0	100.0	100.0
Property and Casualty Insurance [Member] | Minimum [Member] | Third Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	200.0	200.0	200.0
Property and Casualty Insurance [Member] | Minimum [Member] | Fourth Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured		350.0	350.0
Property and Casualty Insurance [Member] | Maximum [Member] | Retained [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Amount Retained	50.0	50.0	50.0
Property and Casualty Insurance [Member] | Maximum [Member] | First Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	100.0	100.0	100.0
Property and Casualty Insurance [Member] | Maximum [Member] | Second Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	200.0	200.0	200.0
Property and Casualty Insurance [Member] | Maximum [Member] | Third Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	400.0	350.0	350.0
Property and Casualty Insurance [Member] | Maximum [Member] | Fourth Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured		450.0	450.0
Life and Health Segment - Property Insurance Operations [Member] | Retained [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage			0.00%
Life and Health Segment - Property Insurance Operations [Member] | First Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Percentage			70.00%
Life and Health Segment - Property Insurance Operations [Member] | Second Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Percentage			70.00%
Life and Health Segment - Property Insurance Operations [Member] | Minimum [Member] | Retained [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Amount Retained			0
Life and Health Segment - Property Insurance Operations [Member] | Minimum [Member] | First Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			8.0
Life and Health Segment - Property Insurance Operations [Member] | Minimum [Member] | Second Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			15.0
Life and Health Segment - Property Insurance Operations [Member] | Maximum [Member] | Retained [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Amount Retained			8.0
Life and Health Segment - Property Insurance Operations [Member] | Maximum [Member] | First Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			15.0
Life and Health Segment - Property Insurance Operations [Member] | Maximum [Member] | Second Layer of Coverage [Member]
Liability for Catastrophe Claims [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			40.0