CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Paid-In Capital	Accumulated Other Comprehensive Income	Retained Earnings
Balance (in shares) at Dec. 31, 2019		476,882	(78,957)
Balance at beginning of period at Dec. 31, 2019	$ 2,151,487	$ 47,688	$ (1,823,201)	$ 1,782,427	$ 1,360	$ 2,143,213
Increase (Decrease) in Stockholders' Equity
Net income	53,910					53,910
Stock amortization and vesting (in shares)		651
Stock amortization and vesting	2,951	$ 65		2,886
Cash dividends	(39,817)					(39,817)
Other comprehensive loss	(136)				(136)
Balance (in shares) at Mar. 31, 2020		477,533	(78,957)
Balance at end of period at Mar. 31, 2020	2,168,395	$ 47,753	$ (1,823,201)	1,785,313	1,224	2,157,306
Balance (in shares) at Dec. 31, 2019		476,882	(78,957)
Balance at beginning of period at Dec. 31, 2019	2,151,487	$ 47,688	$ (1,823,201)	1,782,427	1,360	2,143,213
Increase (Decrease) in Stockholders' Equity
Net income	69,323
Balance (in shares) at Sep. 30, 2020		477,537	(78,957)
Balance at end of period at Sep. 30, 2020	2,118,488	$ 47,754	$ (1,823,201)	1,800,002	929	2,093,004
Balance (in shares) at Mar. 31, 2020		477,533	(78,957)
Balance at beginning of period at Mar. 31, 2020	2,168,395	$ 47,753	$ (1,823,201)	1,785,313	1,224	2,157,306
Increase (Decrease) in Stockholders' Equity
Net income	30,374					30,374
Stock amortization and vesting (in shares)		2
Stock amortization and vesting	7,219	$ 1		7,218
Cash dividends	(39,858)					(39,858)
Other comprehensive loss	(151)				(151)
Balance (in shares) at Jun. 30, 2020		477,535	(78,957)
Balance at end of period at Jun. 30, 2020	2,165,979	$ 47,754	$ (1,823,201)	1,792,531	1,073	2,147,822
Increase (Decrease) in Stockholders' Equity
Net income	(14,961)					(14,961)
Stock amortization and vesting (in shares)		2
Stock amortization and vesting	7,471	$ 0		7,471
Cash dividends	(39,857)					(39,857)
Other comprehensive loss	(144)				(144)
Balance (in shares) at Sep. 30, 2020		477,537	(78,957)
Balance at end of period at Sep. 30, 2020	2,118,488	$ 47,754	$ (1,823,201)	1,800,002	929	2,093,004
Balance (in shares) at Dec. 31, 2020		477,829	(78,957)
Balance at beginning of period at Dec. 31, 2020	2,215,707	$ 47,783	$ (1,823,201)	1,804,354	2,419	2,184,352
Increase (Decrease) in Stockholders' Equity
Net income	126,354					126,354
Stock amortization and vesting (in shares)		548
Stock amortization and vesting	3,933	$ 55		3,878
Cash dividends	(39,887)					(39,887)
Other comprehensive loss	(137)				(137)
Balance (in shares) at Mar. 31, 2021		478,377	(78,957)
Balance at end of period at Mar. 31, 2021	2,305,970	$ 47,838	$ (1,823,201)	1,808,232	2,282	2,270,819
Balance (in shares) at Dec. 31, 2020		477,829	(78,957)
Balance at beginning of period at Dec. 31, 2020	2,215,707	$ 47,783	$ (1,823,201)	1,804,354	2,419	2,184,352
Increase (Decrease) in Stockholders' Equity
Net income	219,532
Balance (in shares) at Sep. 30, 2021		478,621	(78,957)
Balance at end of period at Sep. 30, 2021	2,326,112	$ 47,862	$ (1,823,201)	1,823,373	2,007	2,276,071
Balance (in shares) at Mar. 31, 2021		478,377	(78,957)
Balance at beginning of period at Mar. 31, 2021	2,305,970	$ 47,838	$ (1,823,201)	1,808,232	2,282	2,270,819
Increase (Decrease) in Stockholders' Equity
Net income	30,464					30,464
Stock amortization and vesting (in shares)		244
Stock amortization and vesting	7,562	$ 24		7,538
Cash dividends	(43,963)					(43,963)
Other comprehensive loss	(138)				(138)
Balance (in shares) at Jun. 30, 2021		478,621	(78,957)
Balance at end of period at Jun. 30, 2021	2,299,895	$ 47,862	$ (1,823,201)	1,815,770	2,144	2,257,320
Increase (Decrease) in Stockholders' Equity
Net income	62,714					62,714
Stock amortization and vesting (in shares)		0
Stock amortization and vesting	7,603	$ 0		7,603
Cash dividends	(43,963)					(43,963)
Other comprehensive loss	(137)				(137)
Balance (in shares) at Sep. 30, 2021		478,621	(78,957)
Balance at end of period at Sep. 30, 2021	$ 2,326,112	$ 47,862	$ (1,823,201)	$ 1,823,373	$ 2,007	$ 2,276,071