Unsecured Borrowings - Schedule of Short Term and Long Term Unsecured Borrowings (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Short-term
Unsecured short-term borrowings	$ 48,990	$ 52,870
Long-term
Unsecured borrowings	242,780	213,481
Total	$ 291,770	$ 266,351

Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Name:	us-gaap_UnsecuredLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant