Netting Arrangements (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Assets
Derivative assets, gross amount	$ 5,742	$ 6,643
Derivative assets, gross amount offset	(4,050)	(5,186)
Derivative assets, net amount presented in the condensed consolidated balance sheets	1,692	1,457
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	(224)	(116)
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	(40)
Derivative assets, net amount	1,468	1,301
Securities purchased under agreements to resell or similar arrangements, gross amount	37,160	47,550
Securities purchased under agreements to resell or similar arrangements, gross amount offset	0	0
Securities purchased under agreements to resell or similar arrangements, net amount presented in the condensed consolidated balance sheets	37,160	47,550
Securities purchased under agreements to resell, under master netting arrangement, amounts not offset in the condensed consolidated balance sheets, financial instruments	0	0
Securities purchased under agreements to resell or similar arrangements, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	(37,160)	(47,550)
Securities purchased under agreements to resell or similar arrangements, net amount	0	0
Total assets, gross amount	42,902	54,193
Total assets, gross amount offset	(4,050)	(5,186)
Total assets, net amount presented in the condensed consolidated balance sheets	38,852	49,007
Total assets, under master netting arrangements, not offset in the condensed consolidated balance sheets, financial instruments	(224)	(116)
Total assets, under master netting arrangements, not offset in the condensed consolidated balance sheets, collateral	(37,160)	(47,590)
Total assets, net amount	1,468	1,301
Liabilities:
Derivative liabilities, gross amount	(8,538)	(10,807)
Derivative liabilities, gross amount offset	7,728	10,194
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	(810)	(613)
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	224	116
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	0
Derivative liabilities, net amount	(586)	(497)
Securities sold under agreements to repurchase, gross amount		(50)
Securities sold under agreements to repurchase, gross amount offset		0
Securities sold under agreements to repurchase, net amount presented in the condensed consolidated balance sheets		(50)
Securities sold under agreements to repurchase, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments		0
Securities sold under agreements to repurchase, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral		50
Securities sold under agreements to repurchase, net amount		0
Total liabilities, gross amount	(8,538)	(10,857)
Total liabilities, gross amount offset	7,728	10,194
Total liabilities, net amount presented in the condensed consolidated balance sheets	(810)	(663)
Total liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	224	116
Total liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	50
Total liabilities, net amount	(586)	(497)
Risk Management Derivatives [Member]
Assets
Derivative assets, gross amount offset	(4,050)	(5,186)
Liabilities:
Derivative liabilities, gross amount offset	7,728	10,194
Risk Management Derivatives [Member] | OTC Risk Management Derivatives [Member]
Assets
Derivative assets, gross amount	4,355	5,461
Derivative assets, gross amount offset	(4,354)	(5,428)
Derivative assets, net amount presented in the condensed consolidated balance sheets	1	33
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	0	0
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	(33)
Derivative assets, net amount	1	0
Liabilities:
Derivative liabilities, gross amount	(6,172)	(7,836)
Derivative liabilities, gross amount offset	5,754	7,567
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	(418)	(269)
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	0	0
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	0
Derivative liabilities, net amount	(418)	(269)
Risk Management Derivatives [Member] | Cleared Risk Management Derivatives [Member]
Assets
Derivative assets, gross amount	954	927
Derivative assets, gross amount offset	304	242
Derivative assets, net amount presented in the condensed consolidated balance sheets	1,258	1,169
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	0	0
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	0
Derivative assets, net amount	1,258	1,169
Liabilities:
Derivative liabilities, gross amount	(1,974)	(2,627)
Derivative liabilities, gross amount offset	1,974	2,627
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	0	0
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	0	0
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	0
Derivative liabilities, net amount	0	0
Mortgage commitment derivatives [Member]
Assets
Derivative assets, gross amount	433	255
Derivative assets, gross amount offset	0	0
Derivative assets, net amount presented in the condensed consolidated balance sheets	433	255
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	(224)	(116)
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	(7)
Derivative assets, net amount	209	132
Liabilities:
Derivative liabilities, gross amount	(392)	(344)
Derivative liabilities, gross amount offset	0	0
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	(392)	(344)
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	224	116
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	0	0
Derivative liabilities, net amount	$ (168)	$ (228)