STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) - $ / shares	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Class A common stock
Dividends declared (in dollars per share)	$ 1.035	$ 1.035	$ 0.965	$ 0.965	$ 2.070	$ 1.930
Class B common stock
Dividends declared (in dollars per share)	$ 155.25	$ 155.25	$ 144.75	$ 144.75	$ 310.50	$ 289.50