Investments and Related Matters Investment Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Schedule of Investments [Line Items]
Investments	$ 9,875		$ 9,875		$ 15,351
Securities sold, not yet purchased, at fair value	1,306		1,306		794
Investment Segment [Member]
Schedule of Investments [Line Items]
Investments	9,217		9,217		14,553
Securities sold, not yet purchased, at fair value	1,306		1,306		794
Portion of trading gains (loss) that relates to trading securities still held	(74)	$ 203	(189)	$ 598
Investment Segment [Member] | Equity securities:
Schedule of Investments [Line Items]
Investments	8,949		8,949		14,324
Securities sold, not yet purchased, at fair value	1,251		1,251		794
Investment Segment [Member] | Corporate debt:
Schedule of Investments [Line Items]
Investments	268		268		72
Investment Segment [Member] | Basic materials | Equity securities:
Schedule of Investments [Line Items]
Investments	927		927		563
Investment Segment [Member] | Communications | Equity securities:
Schedule of Investments [Line Items]
Investments	187		187		407
Investment Segment [Member] | Consumer, non-cyclical | Equity securities:
Schedule of Investments [Line Items]
Investments	3,010		3,010		3,684
Securities sold, not yet purchased, at fair value	4		4		794
Investment Segment [Member] | Consumer, non-cyclical | Corporate debt:
Schedule of Investments [Line Items]
Investments	98		98		0
Investment Segment [Member] | Consumer, cyclical | Equity securities:
Schedule of Investments [Line Items]
Investments	152		152		115
Securities sold, not yet purchased, at fair value	848		848		0
Investment Segment [Member] | Consumer, cyclical | Corporate debt:
Schedule of Investments [Line Items]
Investments	152		152		55
Investment Segment [Member] | Diversified | Equity securities:
Schedule of Investments [Line Items]
Investments	17		17		17
Investment Segment [Member] | Energy | Equity securities:
Schedule of Investments [Line Items]
Investments	1,447		1,447		1,461
Securities sold, not yet purchased, at fair value	136		136		0
Investment Segment [Member] | Energy | Corporate debt:
Schedule of Investments [Line Items]
Securities sold, not yet purchased, at fair value	55		55		0
Investment Segment [Member] | Financial | Equity securities:
Schedule of Investments [Line Items]
Investments	1,931		1,931		2,094
Securities sold, not yet purchased, at fair value	158		158		0
Investment Segment [Member] | Financial | Corporate debt:
Schedule of Investments [Line Items]
Investments	4		4		4
Investment Segment [Member] | Financial | Mortgage-backed securities:
Schedule of Investments [Line Items]
Investments	0		0		157
Investment Segment [Member] | Industrial | Equity securities:
Schedule of Investments [Line Items]
Investments	256		256		188
Securities sold, not yet purchased, at fair value	105		105		0
Investment Segment [Member] | Technology | Equity securities:
Schedule of Investments [Line Items]
Investments	1,022		1,022		5,795
Investment Segment [Member] | Sovereign debt | Corporate debt:
Schedule of Investments [Line Items]
Investments	0		0		13
Investment Segment [Member] | Utilities | Corporate debt:
Schedule of Investments [Line Items]
Investments	$ 14		$ 14		$ 0