Netting Arrangements (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Assets
Derivative assets, gross amount	$ 8,278	$ 4,890
Derivative assets, gross amount offset	(7,530)	(4,024)
Derivative assets, net amount presented in the condensed consolidated balance sheets	748	866
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	(291)	(119)
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	(8)	(21)
Derivative assets, net amount	449	726
Securities purchased under agreements to resell or similar arrangements, gross amount	41,445	37,950
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	41,445	37,950
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	(41,445)	(37,950)
Securities purchased under agreements to resell or similar arrangements, net amount	0	0
Total assets, gross amount	49,723	42,840
Total assets, gross amount offset	(7,530)	(4,024)
Total assets, net amount presented in the condensed consolidated balance sheets	42,193	38,816
Total assets, under master netting arrangements, not offset in the condensed consolidated balance sheets, financial instruments	(291)	(119)
Total assets, under master netting arrangements, not offset in the condensed consolidated balance sheets, collateral	(41,453)	(37,971)
Total assets, net amount	449	726
Liabilities:
Derivative liabilities, gross amount	(15,403)	(9,072)
Derivative liabilities, gross amount offset	14,269	8,650
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	(1,134)	(422)
Derivative Liability, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	291	119
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	31	(1)
Derivative liabilities, net amount	(812)	(304)
Securities sold under agreements to repurchase or similar arrangements, gross amount	(115)	(62)
Securities sold under agreements to repurchase or similar arrangements, gross amount offset	0	0
Securities sold under agreements to repurchase or similar arrangements, net amount presented in the condensed consolidated balance sheets	(115)	(62)
Securities sold under agreements to repurchase or similar arrangements, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	0	0
Securities sold under agreements to repurchase or similar arrangements, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	115	62
Securities sold under agreements to repurchase or similar arrangements, net amount	0	0
Total liabilities, gross amount	(15,518)	(9,134)
Total liabilities, gross amount offset	14,269	8,650
Total liabilities, net amount presented in the condensed consolidated balance sheets	(1,249)	(484)
Total liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	291	119
Total liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	146	61
Total liabilities, net amount	(812)	(304)
Risk Management Derivatives [Member]
Assets
Derivative assets, gross amount offset	(7,530)	(4,024)
Liabilities:
Derivative liabilities, gross amount offset	14,269	8,650
Risk Management Derivatives [Member] | OTC Risk Management Derivatives [Member]
Assets
Derivative assets, gross amount	4,949	4,042
Derivative assets, gross amount offset	(4,925)	(4,021)
Derivative assets, net amount presented in the condensed consolidated balance sheets	24	21
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	(18)
Derivative assets, net amount	24	3
Liabilities:
Derivative liabilities, gross amount	(8,303)	(6,118)
Derivative liabilities, gross amount offset	8,156	5,861
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	(147)	(257)
Derivative Liability, 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	(147)	(257)
Risk Management Derivatives [Member] | Cleared Risk Management Derivatives [Member]
Assets
Derivative assets, gross amount	2,692	708
Derivative assets, gross amount offset	(2,605)	(3)
Derivative assets, net amount presented in the condensed consolidated balance sheets	87	705
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	87	705
Liabilities:
Derivative liabilities, gross amount	(6,142)	(2,796)
Derivative liabilities, gross amount offset	6,113	2,789
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	(29)	(7)
Derivative Liability, 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	29	0
Derivative liabilities, net amount	0	(7)
Mortgage commitment derivatives [Member]
Assets
Derivative assets, gross amount	637	140
Derivative assets, gross amount offset	0	0
Derivative assets, net amount presented in the condensed consolidated balance sheets	637	140
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	(291)	(119)
Derivative assets, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	(8)	(3)
Derivative assets, net amount	338	18
Liabilities:
Derivative liabilities, gross amount	(958)	(158)
Derivative liabilities, gross amount offset	0	0
Derivative liabilities, net amount presented in the condensed consolidated balance sheets	(958)	(158)
Derivative Liability, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, financial instruments	291	119
Derivative liabilities, under master netting arrangements, amounts not offset in the condensed consolidated balance sheets, collateral	2	(1)
Derivative liabilities, net amount	$ (665)	$ (40)