Fair Value Measurements (Changes in Level 3 Instruments) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	$ 3,110		$ 3,110			$ 2,813
Cash Accruals Not Included In Schedule Assets Measured For Fair Value On Recurring Basis	11	6	11	6
Domestic Corporate Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	3,126	3,207	3,126	3,207	3,071	2,918	3,542	3,552
Net realized/unrealized gains (losses) included in earnings	(13)	(7)	21	(251)
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(57)	4	120	214
Purchases	190	33	343	94
Sales	(157)	(341)	(159)	(347)
Settlements	(27)	(45)	(139)	(90)
Transfers into Level 3	42	15	138	108
Transfers out of Level 3	(63)	0	(116)	(73)
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	560	98	560	98	560	96	90	77
Net realized/unrealized gains (losses) included in earnings	0	0	0	0
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(4)	4	31	(4)
Purchases	4	12	13	16
Sales	(7)	0	(7)	0
Settlements	(1)	0	(8)	(1)
Transfers into Level 3	0	0	435	10
Transfers out of Level 3	0	0	0	0
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Residential Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	66	91	66	91	81	86	96	100
Net realized/unrealized gains (losses) included in earnings	(1)	0	1	0
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(1)	(1)	0	(2)
Purchases	0	0	0	0
Sales	16	(2)	(16)	(2)
Settlements	1	(4)	(5)	(5)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	12	5	12	5	11	10	6	6
Net realized/unrealized gains (losses) included in earnings	0	0	0	0
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	1	(1)	0	(1)
Transfers into Level 3	0	0	2	0
Transfers out of Level 3	0	0	0	0
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	7,277	5,346	7,277	5,346	6,908	6,898	4,916	5,023
Net realized/unrealized gains (losses) included in earnings	(1)	(1)	2	2
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(1)	66	(26)	(68)
Purchases	591	766	996	910
Sales	0	(1)	0	(1)
Settlements	(214)	(263)	(583)	(525)
Transfers into Level 3	0	0	0	12
Transfers out of Level 3	(10)	(7)	(10)	(7)
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Foreign Corporate Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	1,042	1,184	1,042	1,184	1,060	1,052	1,336	1,212
Net realized/unrealized gains (losses) included in earnings	(24)	91	3	(83)
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(33)	(7)	79	20
Purchases	216	1,985	436	2,809
Sales	(64)	0	(66)	(3)
Settlements	(222)	(2,009)	(457)	(2,742)
Transfers into Level 3	1	0	1	15
Transfers out of Level 3	(6)	(44)	(6)	(44)
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Foreign Government Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	1	38	1	38	1	31	41	42
Net realized/unrealized gains (losses) included in earnings	0	0	0	0
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	0	3	0	(4)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	(30)	0
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
US Treasury and Government [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	249	264	249	264	232	225	264	277
Net realized/unrealized gains (losses) included in earnings	0	0	0	0
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(17)	0	26	(13)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	(2)	0
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Retained Interest [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	73	93	73	93	75	72	91	83
Net realized/unrealized gains (losses) included in earnings	(1)	(2)	3	5
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(2)	(6)	5	16
Purchases	0	2	1	2
Sales	0	0	0	0
Settlements	(5)	(8)	(8)	(13)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Available-for-sale Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	9	11	9	11	11	11	11	13
Net realized/unrealized gains (losses) included in earnings	0	0	0	0
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	0	0	0	0
Purchases	2	0	2	0
Sales	(2)	0	(2)	0
Settlements	(2)	0	(2)	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	(2)
Net change in unrealized gains (losses) relating to instruments still held	0	0	0	0
Derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	144	170	144	170	149	163	170	262
Net realized/unrealized gains (losses) included in earnings	4	25	(15)	(63)
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	0	(1)	0	1
Purchases	(1)	(1)	(2)	(2)
Sales	0	0	0	0
Settlements	0	(1)	(1)	(54)
Transfers into Level 3	0	26	(1)	26
Transfers out of Level 3	0	0	0	0
Net change in unrealized gains (losses) relating to instruments still held	4	27	(8)	(34)
Other 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	140	438	140	438	99	293	409	432
Net realized/unrealized gains (losses) included in earnings	(1)	100	3	(102)
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	0	(4)	0	4
Purchases	154	126	237	159
Sales	0	(1)	0	(55)
Settlements	(112)	0	(112)	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	(2)	0	(281)	0
Net change in unrealized gains (losses) relating to instruments still held	0	92	0	(93)
Total [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Level 3	12,699	10,945	12,699	10,945	12,258	11,855	10,972	11,079
Net realized/unrealized gains (losses) included in earnings	(37)	206	18	(492)
Net realized/unrealized gains (losses) included in accumulated other comprehensive income	(115)	58	235	164
Purchases	1,156	2,923	2,026	3,988
Sales	(246)	(345)	(250)	(408)
Settlements	(583)	(2,331)	(1,315)	(3,431)
Transfers into Level 3	43	41	575	171
Transfers out of Level 3	(81)	(51)	(445)	(126)
Net change in unrealized gains (losses) relating to instruments still held	$ 4	$ 119	$ (8)	$ (127)