Investments OTTI (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 securities	Dec. 31, 2012 securities	Dec. 31, 2011 securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	$ 5.9	$ 10.9	$ 107.3
No. of Securities	42	43	166
U.S. corporate
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0	2.9	20.4
No. of Securities	0	3	17
Foreign
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	1.8	0.8	27.8
No. of Securities	1	3	50
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	3.4	6.0	8.2
No. of Securities	35	33	38
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0.3	0	28.2
No. of Securities	3	0	8
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0.3	1.2	22.7
No. of Securities	2	4	53
Equity securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0.1	0	0
No. of Securities	1	0	0
Intent related impairment
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	9	8	128
Write-down related to intent impairments	1.1	1.8	89.7
Intent related impairment | U.S. corporate
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	0	1	17
Write-down related to intent impairments	0	0.2	20.4
Intent related impairment | Foreign
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	0	3	46
Write-down related to intent impairments	0	0.8	23.7
Intent related impairment | Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	6	3	7
Write-down related to intent impairments	0.8	0.7	1.6
Intent related impairment | Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	3	0	8
Write-down related to intent impairments	0.3	0	22.9
Intent related impairment | Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	0	1	50
Write-down related to intent impairments	0	0.1	21.1
Credit related impairment
Available-for-sale Securities Including Securities Pledged [Line Items]
Write-downs related to credit impairments	$ 4.8	$ 9.1	$ 17.6