Fair Value Of Financial Instruments (Aggregate Fair Value And Remaining Contractual Principal Balance Outstanding On Fair Value Option) (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Residential Mortgage Loans [Member] | Loans Receivable [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Loans receivable and other instruments, contractual outstanding principal	$ 72	$ 89
Loans receivable and other instruments, 90 days or more past due, contractual outstanding principal	145	147
Loans receivable and other instruments, fair value	72	89
Loans receivable and other instruments, 90 days or more past due, fair value	57	31
Loans receivable and other instruments, difference	0	0
Loans receivable and other instruments, 90 days or more past due, difference	88	116
Total Loans Receivable and Other Instruments [Member] | Loans Receivable [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Loans receivable and other instruments, contractual outstanding principal	217	236
Loans receivable and other instruments, fair value	129	120
Loans receivable and other instruments, difference	88	116
Variable Interest Entity Notes [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Long-term debt instruments, contractual outstanding principal	951	1,117
Long-term debt instruments, fair value	321	350
Long-term debt instruments, difference	630	767
Medium Term Notes [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Long-term debt instruments, contractual outstanding principal	119	122
Long-term debt instruments, fair value	105	110
Long-term debt instruments, difference	$ 14	$ 12