Stockholders' Equity (Narrative) (Details) - USD ($) shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Apr. 30, 2021	Jul. 30, 2020
Stockholders Equity Note [Line Items]
Repurchases of capital stock	$ 12,796,000,000	$ 6,852,000,000	$ 24,191,000,000	$ 15,348,000,000
Class C Capital Stock | Share Repurchase Program
Stockholders Equity Note [Line Items]
Authorized share repurchase amount					$ 50,000,000,000.0	$ 28,000,000,000.0
Remaining amount available for repurchase	$ 43,500,000,000		$ 43,500,000,000
Repurchases of capital stock (in shares)	5.4		11.1
Repurchases of capital stock	$ 12,800,000,000		$ 24,200,000,000