Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies - Other Supplemental Lease Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Operating leases, weighted-average remaining contractual lease term	7 years 1 month 6 days
Operating lease, weighted-average discount rate	3.70%
Operating cash flows from operating leases	$ 156
ROU assets obtained in exchange for new operating lease liabilities	$ 122