Leases (Lessee Components of Lease Expense) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property leases
Operating lease expense	$ 139	$ 185
Variable lease expense	54	36
Total property lease expense	193	$ 221
Minimum annual guaranteed rent in excess of concession fees	$ 19