Investments (Details 7) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Investments in limited partnerships
Equity in earnings of limited partnerships	$ 28,000,000	$ 50,000,000
Asset recorded	915,000,000us-gaap_EquityMethodInvestments		979,000,000us-gaap_EquityMethodInvestments
Income (loss) recognized due to valuation adjustments by the partnerships	(39,000,000)		7,000,000
Income (loss) recorded	67,000,000		106,000,000
Per the limited partner financial statements
Total partnership assets	43,000,000,000		45,000,000,000
Total partnership liabilities	4,000,000,000		4,000,000,000
Total partnership valuation adjustment gains (losses)	(400,000,000)		(1,000,000,000)
Total partnership net income	1,600,000,000		7,000,000,000
Indemnity
Investments in limited partnerships
Equity in earnings of limited partnerships	2,000,000	6,000,000
Number of partnerships	58		58
Asset recorded	100,000,000		113,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(10,000,000)		2,000,000
Income (loss) recorded	12,000,000		9,000,000
Valuation change of equity method investment expected to be recorded next quarter	7,000,000
Indemnity \| Private equity
Investments in limited partnerships
Number of partnerships	27		27
Asset recorded	49,000,000		52,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(1,000,000)		(4,000,000)
Income (loss) recorded	1,000,000		8,000,000
Indemnity \| Private equity \| Less than 10%
Investments in limited partnerships
Number of partnerships	24		24
Asset recorded	32,000,000		34,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(1,000,000)		(7,000,000)
Income (loss) recorded	1,000,000		7,000,000
Indemnity \| Private equity \| Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	17,000,000		18,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		3,000,000
Income (loss) recorded	0		1,000,000
Indemnity \| Mezzanine debt
Investments in limited partnerships
Number of partnerships	15		15
Asset recorded	14,000,000		14,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	1,000,000		2,000,000
Indemnity \| Mezzanine debt \| Less than 10%
Investments in limited partnerships
Number of partnerships	11		11
Asset recorded	9,000,000		10,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	1,000,000		2,000,000
Indemnity \| Mezzanine debt \| Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	5,000,000		4,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		0
Income (loss) recorded	0		0
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		16
Asset recorded	37,000,000		47,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(9,000,000)		6,000,000
Income (loss) recorded	10,000,000		(1,000,000)
Indemnity \| Real estate \| Less than 10%
Investments in limited partnerships
Number of partnerships	11		11
Asset recorded	25,000,000		36,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(5,000,000)		5,000,000
Income (loss) recorded	5,000,000		(2,000,000)
Indemnity \| Real estate \| Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	3,000,000		4,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(6,000,000)		1,000,000
Income (loss) recorded	5,000,000		0
Indemnity \| Real estate \| Greater than 50%
Investments in limited partnerships
Number of partnerships	2		2
Asset recorded	9,000,000		7,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	2,000,000		0
Income (loss) recorded	0		1,000,000
Exchange
Investments in limited partnerships
Equity in earnings of limited partnerships	26,000,000	44,000,000
Number of partnerships	104		102
Asset recorded	815,000,000		866,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(29,000,000)		5,000,000
Income (loss) recorded	55,000,000		97,000,000
Valuation change of equity method investment expected to be recorded next quarter	28,000,000
Exchange \| Private equity
Investments in limited partnerships
Number of partnerships	45		45
Asset recorded	404,000,000		418,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(7,000,000)		1,000,000
Income (loss) recorded	15,000,000		46,000,000
Exchange \| Private equity \| Less than 10%
Investments in limited partnerships
Number of partnerships	42		42
Asset recorded	333,000,000		344,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(8,000,000)		(12,000,000)
Income (loss) recorded	15,000,000		43,000,000
Exchange \| Private equity \| Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	71,000,000		74,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		13,000,000
Income (loss) recorded	0		3,000,000
Exchange \| Mezzanine debt
Investments in limited partnerships
Number of partnerships	28		28
Asset recorded	172,000,000		170,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(2,000,000)		(3,000,000)
Income (loss) recorded	8,000,000		22,000,000
Exchange \| Mezzanine debt \| Less than 10%
Investments in limited partnerships
Number of partnerships	21		21
Asset recorded	118,000,000		120,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(3,000,000)		0
Income (loss) recorded	6,000,000		16,000,000
Exchange \| Mezzanine debt \| Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	4		4
Asset recorded	25,000,000		23,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	0		(3,000,000)
Income (loss) recorded	2,000,000		3,000,000
Exchange \| Mezzanine debt \| Greater than 50%
Investments in limited partnerships
Number of partnerships	3		3
Asset recorded	29,000,000		27,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	1,000,000		0
Income (loss) recorded	0		3,000,000
Exchange \| Real estate
Investments in limited partnerships
Number of partnerships	31		29
Asset recorded	239,000,000		278,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(20,000,000)		7,000,000
Income (loss) recorded	32,000,000		29,000,000
Exchange \| Real estate \| Less than 10%
Investments in limited partnerships
Number of partnerships	24		22
Asset recorded	162,000,000		207,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(11,000,000)		18,000,000
Income (loss) recorded	16,000,000		7,000,000
Exchange \| Real estate \| Greater than or equal to 10% but less than 50%
Investments in limited partnerships
Number of partnerships	5		5
Asset recorded	42,000,000		44,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	(18,000,000)		6,000,000
Income (loss) recorded	16,000,000		2,000,000
Exchange \| Real estate \| Greater than 50%
Investments in limited partnerships
Number of partnerships	2		2
Asset recorded	35,000,000		27,000,000
Income (loss) recognized due to valuation adjustments by the partnerships	9,000,000		(17,000,000)
Income (loss) recorded	$ 0		$ 20,000,000

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