Leases Schedule of supplemental balance sheet information related to operating leases (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019
Lessor, Lease, Description [Line Items]
Document Period End Date	Sep. 30, 2019
Operating Lease, Right-of-Use Asset	$ 1,178
Operating Lease, Liability, Current	260
Operating Lease, Liability, Noncurrent	969
Operating Lease, Liability	$ 1,229
Operating Lease, Weighted Average Remaining Lease Term	9 years
Operating Lease, Weighted Average Discount Rate, Percent	3.07%
Accounting Standards Update 2016-02 [Member]
Lessor, Lease, Description [Line Items]
Operating Lease, Liability	$ 1,229	$ 1,064