Investments - OTTI (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 securities		Dec. 31, 2011 securities		Dec. 31, 2010 securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	$ 10,900,000		$ 107,300,000		$ 147,100,000
No. of Securities	43		166		154
Fair value of fixed maturies with OTTI	1,200,000,000		1,900,000,000
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0		0		1,700,000
No. of Securities	0		0		1
U.S. corporate securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	2,900,000		20,400,000		6,600,000
No. of Securities	3		17		24
Foreign
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	800,000	[1]	27,800,000	[1]	42,400,000	[1]
No. of Securities	3	[1]	50	[1]	20	[1]
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	6,000,000		8,200,000		14,800,000
No. of Securities	33		38		53
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0		28,200,000		20,500,000
No. of Securities	0		8		8
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	1,200,000		22,700,000		58,500,000
No. of Securities	4		53		42
Limited partnerships
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0		0		1,600,000
No. of Securities	0		0		4
Equity securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0		0		0	[2]
No. of Securities	0		0		1
Mortgage loans on real estate
Available-for-sale Securities Including Securities Pledged [Line Items]
Impairment	0		0		1,000,000
No. of Securities	0		0		1
Credit related impairment
Available-for-sale Securities Including Securities Pledged [Line Items]
Write-downs related to credit impairments	9,100,000		17,600,000		48,400,000
Intent related impairment
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	8		128		90
Write-down related to intent impairments	1,800,000		89,700,000		98,700,000
Intent related impairment | U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	0		0		1
Write-down related to intent impairments	0		0		1,700,000
Intent related impairment | U.S. corporate securities
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	1		17		24
Write-down related to intent impairments	200,000		20,400,000		6,700,000
Intent related impairment | Foreign
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	3	[1]	46	[1]	15	[1]
Write-down related to intent impairments	800,000	[1]	23,700,000	[1]	28,500,000	[1]
Intent related impairment | Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	3		7		18
Write-down related to intent impairments	700,000		1,600,000		8,600,000
Intent related impairment | Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	0		8		6
Write-down related to intent impairments	0		22,900,000		16,200,000
Intent related impairment | Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
No. of Securities	1		50		26
Write-down related to intent impairments	$ 100,000		$ 21,100,000		$ 37,000,000

[1] Primarily U.S. dollar denominated.

[2] Less than $01.