Pledged Assets (Offsetting Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Offsetting Assets and Liabilities [Line Items]
Collateral Received	$ (644)
Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	5,627	$ 1,761
Gross Amount Offset in the Consolidated Balance Sheets	(175)
Net Amounts of Assets Presented in the Consolidated Balance Sheets	5,452	1,761
Financial Instruments	(4,808)	(1,387)
Collateral Received		(357)
Net Amount	0	17
Assets [Member] | ERROR in label resolution.
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	11	48
Net Amounts of Assets Presented in the Consolidated Balance Sheets	11	48
Financial Instruments	(11)	(31)
Collateral Received	0	0
Net Amount	0	17
Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	41,822	46,427
Gross Amount Offset in the Consolidated Balance Sheets	(175)
Net Amounts of Assets Presented in the Consolidated Balance Sheets	41,647	46,427
Financial Instruments	(4,808)	(1,387)
Collateral Received	(36,839)	(45,040)
Net Amount	0
Liability [Member] | Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Net Amount	0
Liability [Member] | ERROR in label resolution.
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	942	920
Net Amounts of Assets Presented in the Consolidated Balance Sheets	942	920
Financial Instruments	(11)	(31)
Collateral Received	(931)	(889)
Net Amount	0	0
Reverse Repurchase Agreements [Member] | Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	5,616	1,713
Gross Amount Offset in the Consolidated Balance Sheets	(175)
Net Amounts of Assets Presented in the Consolidated Balance Sheets	5,441	1,713
Financial Instruments	(4,797)	(1,356)
Collateral Received	(644)	(357)
Repurchase Agreements [Member] | Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	40,880	45,507
Gross Amount Offset in the Consolidated Balance Sheets	(175)
Net Amounts of Assets Presented in the Consolidated Balance Sheets	40,705	45,507
Financial Instruments	(4,797)	(1,356)
Collateral Received	$ (35,908)	$ (44,151)