Offsetting Arrangements - Repo, Sec Lending Transactions Maturity By Category (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	$ 36,379	$ 35,509
Securities lending transactions	10,124	9,424
Gross amount of recognized liabilities for repurchase agreements and securities lending	46,503	44,933
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	36,379	35,509
Securities lending transactions	9,528	8,390
Gross amount of recognized liabilities for repurchase agreements and securities lending	45,907	43,899
Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	0	0
Securities lending transactions	0	0
Gross amount of recognized liabilities for repurchase agreements and securities lending	0	0
30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	0	0
Securities lending transactions	596	1,034
Gross amount of recognized liabilities for repurchase agreements and securities lending	596	1,034
U.S. Treasury and agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	36,379	35,509
U.S. Treasury and agency securities | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	36,379	35,509
U.S. Treasury and agency securities | Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	0	0
U.S. Treasury and agency securities | 30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	0	0
Corporate debt securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	45	53
Corporate debt securities | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	45	53
Corporate debt securities | Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	0	0
Corporate debt securities | 30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	0	0
Equity securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	10,079	9,371
Equity securities | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	9,483	8,337
Equity securities | Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	0	0
Equity securities | 30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities lending transactions	$ 596	$ 1,034