Lease Obligations - Lessee (Lease Costs) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Lease Cost
Total finance lease costs	$ 1
Total operating lease costs	29
Total lease costs	30
Net occupancy and equipment expense
Lease Cost
Amortization of right-of-use assets	1
Interest Expense, Long-Term Debt
Lease Cost
Interest on lease liabilities	0
Net occupancy expense
Lease Cost
Operating lease cost	22
Short-term lease cost	0
Variable lease cost	8
Sublease income	$ (1)