Lease Commitments (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liabilities	$ 4,048
Right-of-use assets and lease liabilities, percent recognized from joint venture	100.00%
Future undiscounted cash flows for operating leases not yet commenced	$ 872
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liabilities		$ 2,000