Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($)	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, shares at Dec. 31, 2020		17,092,432
Restricted stock awards, net of forfeitures, shares		(109,054)
Common stock repurchased, shares	(2,277,817)	(2,277,817)
Restricted stock units converted to common stock, shares		11,416
Balance, shares at Sep. 30, 2021		14,716,977
Balance at Dec. 31, 2020	$ 2,302,500,000	$ 200,000	$ 161,900,000	$ 2,138,800,000	$ 1,600,000
Net income	740,700,000	0	0	740,700,000	0
Other comprehensive loss	(900,000)	0	0	0	(900,000)
Stock-based compensation	5,400,000	0	5,400,000	0	0
Common stock repurchased, value	(1,093,900,000)	100,000	(1,300,000)	(1,092,500,000)	0
Balance at Sep. 30, 2021	1,953,800,000	$ 100,000	166,000,000.0	1,787,000,000	700,000
Balance, shares at Jun. 30, 2021		16,003,249
Restricted stock awards, net of forfeitures, shares		(26)
Common stock repurchased, shares		(1,286,246)
Balance, shares at Sep. 30, 2021		14,716,977
Balance at Jun. 30, 2021	2,393,000,000	$ 200,000	150,800,000	2,241,100,000	900,000
Net income	250,000,000.0	0	0	250,000,000.0	0
Other comprehensive loss	(200,000)	0	0	0	(200,000)
Stock-based compensation	15,200,000	0	15,200,000	0	0
Common stock repurchased, value	(704,200,000)	100,000	0	(704,100,000)	0
Balance at Sep. 30, 2021	$ 1,953,800,000	$ 100,000	166,000,000.0	1,787,000,000	700,000
Balance, shares at Dec. 31, 2021	14,145,888	14,145,888
Common stock repurchased, shares	(1,261,457)	(1,261,457)
Restricted stock units converted to common stock, shares		3,980
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		36,300
Balance, shares at Sep. 30, 2022	12,924,711	12,924,711
Balance at Dec. 31, 2021	$ 1,824,200,000	$ 100,000	197,200,000	1,626,700,000	200,000
Net income	408,500,000	0	0	408,500,000	0
Other comprehensive loss	(3,600,000)	0	0	0	(3,600,000)
Stock-based compensation	26,900,000	0	26,900,000	0	0
Common stock repurchased, value	(679,200,000)	0	(700,000)	(678,500,000)	0
Stock Issued During Period, Value, Stock Options Exercised	12,400,000		12,400,000
Balance at Sep. 30, 2022	$ 1,589,200,000	$ 100,000	235,800,000	1,356,700,000	(3,400,000)
Balance, shares at Jun. 30, 2022		12,975,455
Common stock repurchased, shares		(53,769)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		3,025
Balance, shares at Sep. 30, 2022	12,924,711	12,924,711
Balance at Jun. 30, 2022	$ 1,520,100,000	$ 100,000	225,800,000	1,296,400,000	(2,200,000)
Net income	86,800,000	0	0	86,800,000	0
Other comprehensive loss	(1,200,000)	0	0	0	(1,200,000)
Stock-based compensation	8,700,000	0	8,700,000	0	0
Common stock repurchased, value	(26,500,000)	0	0	(26,500,000)	0
Stock Issued During Period, Value, Stock Options Exercised	1,300,000		1,300,000
Balance at Sep. 30, 2022	$ 1,589,200,000	$ 100,000	$ 235,800,000	$ 1,356,700,000	$ (3,400,000)