Investments Unrealized Capital Losses 1 (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Available-for-sale Securities Including Securities Pledged [Line Items]
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	$ 34.7	$ 13.7
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	283.2	1.7
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	50.9	37.6
Total Unrealized Capital Losses	368.8	53.0
Fair value decline below amortized cost less than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Six months or less below amortized cost, Amortized Cost	2,054.4	1,110.8
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	45.3	19.3
Six months or less below amortized cost, Number of Securities	322	141
More than six months and twelve months or less below amortized cost, Amortized Cost	3,991.4	49.5
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	272.6	2.6
More than six months and twelve months or less below amortized cost, Number of Securities	502	31
More than twelve months below amortized cost, Amortized Cost	420.4	198.1
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	37.3	6.2
More than twelve months below amortized cost, Number of Securities	137	99
Total Amortized Cost	6,466.2	1,358.4
Total Unrealized Capital Losses	355.2	28.1
Total Number of Securities	961	271
Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Six months or less below amortized cost, Amortized Cost	24.1	15.2
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	5.3	3.9
Six months or less below amortized cost, Number of Securities	7	10
More than six months and twelve months or less below amortized cost, Amortized Cost	23.5	1.5
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	5.8	0.4
More than six months and twelve months or less below amortized cost, Number of Securities	3	2
More than twelve months below amortized cost, Amortized Cost	9.5	61.6
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	2.5	20.6
More than twelve months below amortized cost, Number of Securities	8	28
Total Amortized Cost	57.1	78.3
Total Unrealized Capital Losses	13.6	24.9
Total Number of Securities	18	40
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	2.1	0.5
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	0.8	0
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	0	0
Total Unrealized Capital Losses	2.9	0.5
U.S. Treasuries | Fair value decline below amortized cost less than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	161.5	300.5
Total Unrealized Capital Losses	2.9	0.5
Total Number of Securities	4	2
U.S. Treasuries | Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	0	0
Total Unrealized Capital Losses	0	0
Total Number of Securities	0	0
U.S. corporate, state and municipalities
Available-for-sale Securities Including Securities Pledged [Line Items]
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	22.9	6.8
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	183.8	0.9
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	32.2	3.4
Total Unrealized Capital Losses	238.9	11.1
U.S. corporate, state and municipalities | Fair value decline below amortized cost less than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	3,869.0	558.1
Total Unrealized Capital Losses	233.2	9.1
Total Number of Securities	519	82
U.S. corporate, state and municipalities | Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	22.8	4.7
Total Unrealized Capital Losses	5.7	2.0
Total Number of Securities	2	2
Foreign
Available-for-sale Securities Including Securities Pledged [Line Items]
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	5.7	4.7
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	86.4	0.5
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	7.9	11.2
Total Unrealized Capital Losses	100.0	16.4
Foreign | Fair value decline below amortized cost less than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	1,665.8	242.7
Total Unrealized Capital Losses	95.0	5.7
Total Number of Securities	239	38
Foreign | Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	23.1	36.0
Total Unrealized Capital Losses	5.0	10.7
Total Number of Securities	5	8
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	2.9	1.6
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	12.0	0.3
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	7.8	16.2
Total Unrealized Capital Losses	22.7	18.1
Residential mortgage-backed | Fair value decline below amortized cost less than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	596.9	201.2
Total Unrealized Capital Losses	21.0	10.2
Total Number of Securities	162	124
Residential mortgage-backed | Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	6.8	25.2
Total Unrealized Capital Losses	1.7	7.9
Total Number of Securities	7	24
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	0.9	0.1
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	0	0
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	0	0.1
Total Unrealized Capital Losses	0.9	0.2
Commercial mortgage-backed | Fair value decline below amortized cost less than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	78.8	11.8
Total Unrealized Capital Losses	0.9	0.2
Total Number of Securities	12	8
Commercial mortgage-backed | Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	0	0
Total Unrealized Capital Losses	0	0
Total Number of Securities	0	0
Other asset-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Six Months or Less Below Amortized Cost, Unrealized Capital Loss	0.2	0
More Than Six Months and Twelve Months or Less Below Amortized Cost, Unrealized Capital Loss	0.2	0
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	3.0	6.7
Total Unrealized Capital Losses	3.4	6.7
Other asset-backed | Fair value decline below amortized cost less than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	94.2	44.1
Total Unrealized Capital Losses	2.2	2.4
Total Number of Securities	25	17
Other asset-backed | Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Total Amortized Cost	4.4	12.4
Total Unrealized Capital Losses	$ 1.2	$ 4.3
Total Number of Securities	4	6