Investments (Details 7) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Investments in limited partnerships
Equity in earnings of limited partnerships	$ 50,000,000	$ 36,000,000
Asset recorded	1,098,000,000		1,086,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	4,000,000		(28,000,000)
Income (loss) recorded	46,000,000		189,000,000
Per the limited partner financial statements
Total partnership assets	49,000,000,000		50,000,000,000
Total partnership liabilities	5,000,000,000		5,000,000,000
Total partnership valuation adjustment gains (losses)	100,000,000		2,000,000,000
Total partnership net income	2,000,000,000		7,000,000,000
Indemnity
Investments in limited partnerships
Equity in earnings of limited partnerships	6,000,000	3,000,000
Number of partnerships	59		61
Asset recorded	145,000,000		146,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	3,000,000		(3,000,000)
Income (loss) recorded	3,000,000		25,000,000
Indemnity | Private equity
Investments in limited partnerships
Number of partnerships	28		29
Asset recorded	62,000,000		62,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		(3,000,000)
Income (loss) recorded	3,000,000		9,000,000
Indemnity | Private equity | Less than 10%
Investments in limited partnerships
Number of partnerships	25		26
Asset recorded	43,000,000		46,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(3,000,000)		(6,000,000)
Income (loss) recorded	3,000,000		9,000,000
Indemnity | Private equity | Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	19,000,000		16,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	4,000,000		3,000,000
Income (loss) recorded	0		0
Indemnity | Private equity | Greater than 50%
Investments in limited partnerships
Number of partnerships	0		0
Asset recorded	0		0
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	0		0
Indemnity | Mezzanine debt
Investments in limited partnerships
Number of partnerships	15		15
Asset recorded	19,000,000		20,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	0		3,000,000
Indemnity | Mezzanine debt | Less than 10%
Investments in limited partnerships
Number of partnerships	11		11
Asset recorded	13,000,000		14,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	0		1,000,000
Indemnity | Mezzanine debt | Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	6,000,000		6,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	0		2,000,000
Indemnity | Mezzanine debt | Greater than 50%
Investments in limited partnerships
Number of partnerships	1		1
Asset recorded	0		0
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	0		0
Indemnity | Real estate
Investments in limited partnerships
Number of partnerships	16		17
Asset recorded	64,000,000		64,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	2,000,000		0
Income (loss) recorded	0		13,000,000
Indemnity | Real estate | Less than 10%
Investments in limited partnerships
Number of partnerships	11		12
Asset recorded	43,000,000		44,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		0
Income (loss) recorded	0		5,000,000
Indemnity | Real estate | Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	15,000,000		14,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		(1,000,000)
Income (loss) recorded	0		4,000,000
Indemnity | Real estate | Greater than 50%
Investments in limited partnerships
Number of partnerships	2		2
Asset recorded	6,000,000		6,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		1,000,000
Income (loss) recorded	0		4,000,000
Exchange
Investments in limited partnerships
Equity in earnings of limited partnerships	44,000,000	33,000,000
Number of partnerships	101		103
Asset recorded	953,000,000		940,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		(25,000,000)
Income (loss) recorded	43,000,000		164,000,000
Exchange | Private equity
Investments in limited partnerships
Number of partnerships	46		47
Asset recorded	468,000,000		463,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	8,000,000		(11,000,000)
Income (loss) recorded	19,000,000		81,000,000
Exchange | Private equity | Less than 10%
Investments in limited partnerships
Number of partnerships	43		44
Asset recorded	389,000,000		396,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(6,000,000)		(24,000,000)
Income (loss) recorded	19,000,000		79,000,000
Exchange | Private equity | Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	79,000,000		67,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	14,000,000		13,000,000
Income (loss) recorded	0		2,000,000
Exchange | Private equity | Greater than 50%
Investments in limited partnerships
Number of partnerships	0		0
Asset recorded	0		0
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	0		0
Exchange | Mezzanine debt
Investments in limited partnerships
Number of partnerships	26		26
Asset recorded	170,000,000		172,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		(1,000,000)
Income (loss) recorded	6,000,000		23,000,000
Exchange | Mezzanine debt | Less than 10%
Investments in limited partnerships
Number of partnerships	19		19
Asset recorded	115,000,000		117,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		1,000,000
Income (loss) recorded	3,000,000		13,000,000
Exchange | Mezzanine debt | Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	4		4
Asset recorded	24,000,000		23,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(2,000,000)		(3,000,000)
Income (loss) recorded	2,000,000		7,000,000
Exchange | Mezzanine debt | Greater than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	31,000,000		32,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		1,000,000
Income (loss) recorded	1,000,000		3,000,000
Exchange | Real estate
Investments in limited partnerships
Number of partnerships	29		30
Asset recorded	315,000,000		305,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(7,000,000)		(13,000,000)
Income (loss) recorded	18,000,000		60,000,000
Exchange | Real estate | Less than 10%
Investments in limited partnerships
Number of partnerships	20		22
Asset recorded	211,000,000		211,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	5,000,000		(10,000,000)
Income (loss) recorded	4,000,000		34,000,000
Exchange | Real estate | Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	7		6
Asset recorded	79,000,000		71,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		(2,000,000)
Income (loss) recorded	1,000,000		10,000,000
Exchange | Real estate | Greater than 50%
Investments in limited partnerships
Number of partnerships	2		2
Asset recorded	25,000,000		23,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(12,000,000)		(1,000,000)
Income (loss) recorded	$ 13,000,000		$ 16,000,000