Business, Basis of Presentation and Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of segments | Segment	6
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums and Other Receivables, Net	$ 25,916	$ 26,081
Payables For Collateral Under Securities Loaned And Other Transactions	32,899	33,264
Derivative assets	12,278	15,761
Derivative liabilities	8,399	10,804
Accrued Investment Income Receivable	3,984	3,988
Other Liabilities	27,232	$ 28,818
CME update impact [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums and Other Receivables, Net	991
Payables For Collateral Under Securities Loaned And Other Transactions	816
Derivative assets	1,800
Derivative liabilities	2,000
Accrued Investment Income Receivable	101
Other Liabilities	$ 14