Loans, Lending Commitments and Allowance for Credit Losses - Impaired Loans and Lending Commitments before Allowance (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Loans
With allowance	$ 229	$ 24
Without allowance	108	101
Total impaired loans	337	125
UPB	351	133
Lending commitments
With allowance	7	19
Without allowance	40	34
Total impaired lending commitments	47	53
Corporate
Loans
With allowance	229	24
Without allowance	26	32
Total impaired loans	255	56
UPB	262	63
Lending commitments
With allowance	7	19
Without allowance	40	34
Total impaired lending commitments	47	53
Consumer
Loans
With allowance	0	0
Without allowance	5	0
Total impaired loans	5	0
UPB	5	0
Lending commitments
With allowance	0	0
Without allowance	0	0
Total impaired lending commitments	0	0
Residential real estate
Loans
With allowance	0	0
Without allowance	77	69
Total impaired loans	77	69
UPB	84	70
Lending commitments
With allowance	0	0
Without allowance	0	0
Total impaired lending commitments	$ 0	$ 0