Other Assets and Liabilites - Schedule of Right of Use Assets and Future Maturities of Lease Liabilities (Details) $ in Millions	Mar. 31, 2019 USD ($)
Right of Use Assets
Right-of-Use Asset, Operating Lease	$ 822
Right-of-Use Asset, Finance Lease	19
Operating Lease Liabilities, Payments Due
2019, Operating Leases	138
2020, Operating Leases	188
2021, Operating Leases	164
2022, Operating Leases	139
2023, Operating Lease	109
2024, Operating Leases	85
Thereafter, Operating Leases	264
Total lease payments, Operating Leases	1,087
Less: imputed interest, Operating Lease	128
Total lease liabilities, Operating Leases	$ 959
Weighted Average Remaining Lease Term, Operating Lease	7 years 6 months
Weighted Average Discount Rate, Percent, Operating Lease	3.10%
Finance Lease Liabilities, Payments, Due
2019, Finance Leases	$ 6
2020, Finance Leases	7
2021, Finance Leases	6
2022, Finance Leases	5
2023, Finance Lease	3
2024, Finance Leases	2
Thereafter, Finance Leases	3
Total lease payments, Finance Leases	32
Less: imputed interest, Finance Leases	5
Total lease liabilities, Finance Leases	$ 27
Weighted Average Remaining Lease Term, Finance Lease	5 years 1 month 6 days
Weighted Average Discount Rate, Percent, Finance Lease	7.00%