Schedule 4 - Reinsurance Schedule (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 2,105.6	$ 2,170.6	$ 2,287.6
Ceded to Other Companies	42.5	40.7	43.9
Assumed from Other Companies	44.0	43.7	45.7
Net Amount	2,107.1	2,173.6	2,289.4
Percentage of Amount Assumed to Net	2.10%	2.00%	2.00%
Life Insurance in Force [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	21,340.4	21,627.8	21,909.4
Ceded to Other Companies	610.4	662.0	695.3
Assumed from Other Companies	242.9	256.9	272.6
Net Amount	20,972.9	21,222.7	21,486.7
Percentage of Amount Assumed to Net	1.20%	1.20%	1.30%
Life Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	392.8	394.3	396.1
Ceded to Other Companies	1.4	1.5	2.0
Assumed from Other Companies	2.0	2.3	2.7
Net Amount	393.4	395.1	396.8
Percentage of Amount Assumed to Net	0.50%	0.60%	0.70%
Accident and Health Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	165.5	166.5	162.0
Ceded to Other Companies	0.4	0.3	0.3
Assumed from Other Companies	0.1	0.1	0.1
Net Amount	165.2	166.3	161.8
Percentage of Amount Assumed to Net	0.10%	0.10%	0.10%
Property, Liability and Casualty Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	1,547.3	1,609.8	1,729.5
Ceded to Other Companies	40.7	38.9	41.6
Assumed from Other Companies	41.9	41.3	42.9
Net Amount	$ 1,548.5	$ 1,612.2	$ 1,730.8
Percentage of Amount Assumed to Net	2.70%	2.60%	2.50%