Offsetting Arrangements - Repo, Sec Lending Transactions Maturity By Category (Details) $ in Millions	Mar. 31, 2016 USD ($)
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	$ 36,530
Securities loaned, gross	9,890
Securities sold and securities loaned under agreements to repurchase, gross	46,420
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	36,530
Securities loaned, gross	8,925
Securities sold and securities loaned under agreements to repurchase, gross	45,455
Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	0
Securities loaned, gross	0
Securities sold and securities loaned under agreements to repurchase, gross	0
30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	0
Securities loaned, gross	965
Securities sold and securities loaned under agreements to repurchase, gross	965
U.S. Treasury and agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	36,454
U.S. Treasury and agency securities | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	36,454
U.S. Treasury and agency securities | Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	0
U.S. Treasury and agency securities | 30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	0
Non-U.S. sovereign debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	76
Securities loaned, gross	114
Non-U.S. sovereign debt | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	76
Securities loaned, gross	114
Non-U.S. sovereign debt | Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	0
Securities loaned, gross	0
Non-U.S. sovereign debt | 30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase, gross	0
Securities loaned, gross	0
Corporate debt securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	1
Corporate debt securities | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	1
Corporate debt securities | Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	0
Corporate debt securities | 30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	0
U.S. equity securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	9,775
U.S. equity securities | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	8,810
U.S. equity securities | Up to 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	0
U.S. equity securities | 30 – 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned, gross	$ 965