Lease Obligations - Lessee - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lessee, Lease, Description [Line Items]
Occupancy Expense	$ 332	$ 292	$ 295
Operating Lease, Impairment Loss	$ 15
Occupancy [Member]
Lessee, Lease, Description [Line Items]
Occupancy Expense		$ 101	$ 101

Amount of net occupancy expense that may include items, such as depreciation of facilities and equipment, lease expenses, property taxes and property and casualty insurance expense.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14(b))
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.6)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737

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