Business, Basis of Presentation and Summary of Significant Accounting Policies (New Accounting Pronouncements) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)	$ 26,870			$ 26,527	$ 35,547		$ 34,683
Accumulated Other Comprehensive Income (Loss), Net of Tax	2,854	$ 5,634		7,427	$ 8,436	$ 6,396	$ 5,366
Equity securities	1,483			2,513
Debt Securities, Trading, and Equity Securities, FV-NI	13,848			16,745
Derivative assets	7,868			8,551
Derivative liabilities	4,135			4,339
Accrued Investment Income Receivable	3,512			3,524
Premiums and Other Receivables, Net	19,608			18,423
Payables For Collateral Under Securities Loaned And Other Transactions	27,030			25,723
Other Liabilities	$ 24,930			23,982
Adjustments for New Accounting Pronouncement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)			$ (1,200)
Accumulated Other Comprehensive Income (Loss), Net of Tax			1,200
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)			328
Equity securities			$ 1,700
Debt Securities, Trading, and Equity Securities, FV-NI				$ 16,000
LCH update impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Derivative assets		(369)
Derivative liabilities		(203)
Accrued Investment Income Receivable		(14)
Premiums and Other Receivables, Net		(184)
Payables For Collateral Under Securities Loaned And Other Transactions		(365)
Other Liabilities		$ 1