STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) - $ / shares	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Class A common stock
Dividends declared (in dollars per share)	$ 1.035	$ 1.035	$ 1.035	$ 0.965	$ 0.965	$ 0.965	$ 3.105	$ 2.895
Class B common stock
Dividends declared (in dollars per share)	$ 155.25	$ 155.25	$ 155.25	$ 144.75	$ 144.75	$ 144.75	$ 465.75	$ 434.25