Schedule IV - Reinsurance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reinsurance information
Gross amount	$ 3,208.0	$ 3,859.8	$ 4,047.6
Ceded to other companies	320.0	307.8	302.2
Assumed from other companies	3.0	3.5	5.2
Life insurance in force
Reinsurance information
Gross amount	256,880.3	241,996.5	237,454.2
Ceded to other companies	94,839.7	84,403.8	76,507.1
Assumed from other companies	1,814.9	2,051.9	2,328.2
Net amount	163,855.5	159,644.6	163,275.3
Percentage of amount assumed to net (as a percent)	1.10%	1.30%	1.40%
Premiums
Reinsurance information
Gross amount	3,208.0	3,859.8	4,047.6
Ceded to other companies	320.0	307.8	302.2
Assumed from other companies	3.0	3.5	5.2
Net amount	2,891.0	3,555.5	3,750.6
Percentage of amount assumed to net (as a percent)	0.10%	0.10%	0.10%
Life insurance premiums
Reinsurance information
Gross amount	1,493.2	1,437.9	1,389.6
Ceded to other companies	160.9	146.2	140.5
Assumed from other companies	3.0	3.5	5.2
Net amount	1,335.3	1,295.2	1,254.3
Percentage of amount assumed to net (as a percent)	0.20%	0.30%	0.40%
Accident and health insurance premiums
Reinsurance information
Gross amount	1,714.8	2,421.9	2,658.0
Ceded to other companies	159.1	161.6	161.7
Net amount	$ 1,555.7	$ 2,260.3	$ 2,496.3