Offsetting Arrangements - Repo, Sec Lending Transactions Maturity By Category (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	$ 74,346	$ 88,904
Securities lending transactions	18,926	15,590
Gross amount of recognized liabilities for repurchase agreements and securities lending	93,272	104,494
U.S. Treasury and agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	74,346	88,904
Securities lending transactions	136	249
Corporate debt securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	433	278
Equity securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	9,857	6,563
Other
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	8,500	8,500
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	74,346	88,904
Securities lending transactions	18,802	15,453
Gross amount of recognized liabilities for repurchase agreements and securities lending	93,148	104,357
Overnight and Continuous | U.S. Treasury and agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	74,346	88,904
Securities lending transactions	136	249
Overnight and Continuous | Corporate debt securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	433	278
Overnight and Continuous | Equity securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	9,733	6,426
Overnight and Continuous | Other
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	8,500	8,500
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	0	0
Securities lending transactions	124	137
Gross amount of recognized liabilities for repurchase agreements and securities lending	124	137
Up to 30 Days | U.S. Treasury and agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	0	0
Securities lending transactions	0	0
Up to 30 Days | Corporate debt securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	0	0
Up to 30 Days | Equity securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	124	137
Up to 30 Days | Other
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	$ 0	$ 0