Fair Value Measurements (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2012 Investment by class [Member]	Jun. 30, 2011 Investment by class [Member]	Jun. 30, 2012 Investment by class [Member]	Jun. 30, 2011 Investment by class [Member]	Jun. 30, 2012 Derivatives by class [Member]	Jun. 30, 2011 Derivatives by class [Member]	Jun. 30, 2012 Derivatives by class [Member]	Jun. 30, 2011 Derivatives by class [Member]	Jun. 30, 2012 Other Asset Backed Securities [Member] Investment by class [Member]	Jun. 30, 2011 Other Asset Backed Securities [Member] Investment by class [Member]	Jun. 30, 2012 Other Asset Backed Securities [Member] Investment by class [Member]	Jun. 30, 2011 Other Asset Backed Securities [Member] Investment by class [Member]	Jun. 30, 2012 U.S. Agency Obligations [Member] Investment by class [Member]	Jun. 30, 2011 U.S. Agency Obligations [Member] Investment by class [Member]	Jun. 30, 2012 U.S. Agency Obligations [Member] Investment by class [Member]	Jun. 30, 2011 U.S. Agency Obligations [Member] Investment by class [Member]	Jun. 30, 2012 Collateralized debt obligations [Member] Investment by class [Member]	Jun. 30, 2011 Collateralized debt obligations [Member] Investment by class [Member]	Jun. 30, 2012 Collateralized debt obligations [Member] Investment by class [Member]	Jun. 30, 2011 Collateralized debt obligations [Member] Investment by class [Member]	Jun. 30, 2012 Corporate obligations [Member] Investment by class [Member]	Jun. 30, 2011 Corporate obligations [Member] Investment by class [Member]	Jun. 30, 2012 Corporate obligations [Member] Investment by class [Member]	Jun. 30, 2011 Corporate obligations [Member] Investment by class [Member]	Jun. 30, 2012 Interest rate swaps [Member] Derivatives by class [Member]	Jun. 30, 2011 Interest rate swaps [Member] Derivatives by class [Member]	Jun. 30, 2012 Interest rate swaps [Member] Derivatives by class [Member]	Jun. 30, 2011 Interest rate swaps [Member] Derivatives by class [Member]	Jun. 30, 2012 Credit Derivative [Member] Derivatives by class [Member]	Jun. 30, 2011 Credit Derivative [Member] Derivatives by class [Member]	Jun. 30, 2012 Credit Derivative [Member] Derivatives by class [Member]	Jun. 30, 2011 Credit Derivative [Member] Derivatives by class [Member]	Jun. 30, 2012 Call Option on Long Term Debt [Member] Derivatives by class [Member]	Jun. 30, 2011 Call Option on Long Term Debt [Member] Derivatives by class [Member]	Jun. 30, 2012 Call Option on Long Term Debt [Member] Derivatives by class [Member]	Jun. 30, 2011 Call Option on Long Term Debt [Member] Derivatives by class [Member]	Jun. 30, 2012 Variable Interest Entity [Member]	Jun. 30, 2011 Variable Interest Entity [Member]	Jun. 30, 2012 Variable Interest Entity [Member]	Jun. 30, 2011 Variable Interest Entity [Member]	Jun. 30, 2012 Investments contract [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Investments contract [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Investments contract [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Investments contract [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Loan [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Loan [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Loan [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Loan [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Derivatives Liability [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Derivatives Liability [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Derivatives Liability [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Derivatives Liability [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Long-term Debt [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Long-term Debt [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Long-term Debt [Member] Variable Interest Entity [Member]	Jun. 30, 2011 Long-term Debt [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Investments [Member]	Jun. 30, 2011 Investments [Member]	Jun. 30, 2012 Investments [Member]	Jun. 30, 2011 Investments [Member]	Jun. 30, 2012 Other Assets [Member]	Jun. 30, 2011 Other Assets [Member]	Jun. 30, 2012 Other Assets [Member]	Jun. 30, 2011 Other Assets [Member]	Dec. 31, 2010 Other Assets [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Derivatives Assets [Member]	Jun. 30, 2011 Derivatives Assets [Member]	Jun. 30, 2012 Derivatives Assets [Member]	Jun. 30, 2011 Derivatives Assets [Member]
Summary of changes in the Level 3 fair value category
Balance, beginning of period	$ 161,450	$ 200,076	$ 97,522	$ 199,172	$ (355,616)	$ (189,614)	$ (486,775)	$ (195,934)	$ 137,026	$ 160,927	$ 75,886	$ 159,473	$ 1,218	$ 1,186	$ 1,224	$ 1,197	$ 9,839	$ 30,027	$ 12,482	$ 30,433	$ 13,367	$ 7,936	$ 7,930	$ 8,069	$ (222,222)	$ 29,571	$ (302,177)	$ 25,750	$ (201,129)	$ (235,910)	$ (190,653)	$ (221,684)	$ 67,735	$ 16,725	$ 6,055		$ 13,679,955	$ 14,173,322	$ 14,019,216	$ 15,874,571	$ 2,184,665	$ 1,929,691	$ 2,199,338	$ 1,904,361	$ 14,460,077	$ 14,086,858	$ 14,126,994	$ 15,800,918				$ 4,511	$ (2,786,644)	$ (1,872,694)	$ (1,934,642)	$ (1,856,366)	$ 161,450	$ 200,076	$ 97,522	$ 199,172	$ 16,023	$ 19,005	$ 16,779		$ 17,909	$ (355,616)	$ (189,614)	$ (486,775)	$ (195,934)
Additions of VIEs																																						(350,624)		(350,624)														(350,624)		(350,624)
Total gains/(losses) realized and unrealized:
Included in earnings	88	(3,321)	40	(3,371)	(81,290)	(47,923)	41,037	(30,278)					(2)	(2)	(2)	(3)		(3,276)	(2)	(3,282)	90	(43)	44	(86)	(112,904)	(76,255)	(45,035)	(66,432)	(7,416)	24,287	(14,638)	15,384	39,030	4,045	100,710	20,770	91,712	322,535	160,521	279,360	20,103	93,433	(62,713)	64,589	131,807	402,698	298,472	355,316				(4,511)	21,235	(121,798)	(115,328)	(102,927)	88	(3,321)	40	(3,371)	(231)	(554)	(987)	542		(81,290)	(47,923)	41,037	(30,278)
Included in other comprehensive income	(1,588)	4,686	6,225	7,909					(1,696)	(403)	6,376	1,787	(3)	13	(9)	3	190	5,001	291	6,134	(79)	75	(433)	(15)													(256,974)	10,346	171,634	450,301	(42,706)	389	25,437	54,563	(267,190)	5,765	148,667	440,520					54,510	(494)	(8,695)	(52,691)	(1,588)	4,686	6,225	7,909
Purchases
Issuances
Sales		(16,600)		(16,600)														(16,600)		(16,600)																		(16,600)		(16,600)																		(16,600)		(16,600)
Settlements	(89,879)	(1,408)	(92,621)	(3,677)	(70,698)	(24,750)	(61,866)	(36,075)	(84,584)	(756)	(84,584)	(1,492)	(749)	(213)	(749)	(213)	(471)	(439)	(3,213)	(1,972)	(4,075)		(4,075)		39,139	(20,526)	51,225	(26,528)	(3,072)	(4,224)	(6,326)	(9,547)	(106,765)		(106,765)		(227,135)	(61,236)	(457,454)	(271,279)					(86,421)	(52,409)	(335,860)	(258,875)					19,863	17,331	32,893	27,348	(89,879)	(1,408)	(92,621)	(3,677)						(70,698)	(24,750)	(61,866)	(36,075)
Transfers in Level 3			58,905								53,068												5,837														(312,083)	(206,015)	(918,442)	(256,140)													(312,083)	(206,015)	(977,347)	(256,140)			58,905
Transfers out of Level 3	(6,301)		(6,301)										(464)		(464)						(5,837)		(5,837)														650,758	223,322	650,758	280,428													657,059	223,322	657,059	280,428	(6,301)		(6,301)
Deconsolidation of VIEs																																								(1,894,967)								(1,894,967)
Balance, end of period	63,770	183,433	63,770	183,433	(507,604)	(262,287)	(507,604)	(262,287)	50,746	159,768	50,746	159,768		984		984	9,558	14,713	9,558	14,713	3,466	7,968	3,466	7,968	(295,987)	(67,210)	(295,987)	(67,210)	(211,617)	(215,847)	(211,617)	(215,847)		20,770		20,770	13,626,233	14,095,050	13,626,233	14,095,050	2,162,062	2,023,513	2,162,062	2,023,513	14,238,273	14,442,912	14,238,273	14,442,912		0		0	(2,346,060)	(2,310,972)	(2,346,060)	(2,310,972)	63,770	183,433	63,770	183,433	15,792	18,451	15,792	18,451	17,909	(507,604)	(262,287)	(507,604)	(262,287)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date					$ (118,474)	$ (61,643)	$ (72,910)	$ (48,301)																	$ (107,861)	$ (83,407)	$ (46,263)	$ (69,607)	$ (10,613)	$ 17,719	$ (26,647)	$ 536		$ 4,045		$ 20,770	$ 54,440	$ 312,136	$ 47,015	$ 264,708	$ 20,103	$ 93,433	$ (62,713)	$ 64,589	$ 131,807	$ 402,698	$ 298,953	$ 355,316				$ (4,511)	$ 21,235	$ (121,798)	$ (115,328)	$ (102,927)					$ (231)	$ (554)	$ (987)	$ 542		$ (118,474)	$ (61,643)	$ (72,910)	$ (48,301)