CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance (in shares) at Dec. 31, 2018		476,095,000	53,410,000
Balance at beginning of period at Dec. 31, 2018	$ 2,088,159	$ 47,610	$ (1,334,688)	$ 1,763,142	$ 4,437	$ 1,607,658
Increase (Decrease) in Stockholders' Equity
Net income (loss)	262,763					262,763
Stock amortization and vesting (in shares)		682,000
Sale of stock held in rabbi trust	(213)	$ 68		(281)
Purchase of treasury stock	(28)		$ (28)
Cash dividends	(29,605)					(29,605)
Other comprehensive loss	(137)				(137)
Balance (in shares) at Mar. 31, 2019		476,777,000	53,410,000
Balance at end of period at Mar. 31, 2019	2,320,939	$ 47,678	$ (1,334,716)	1,762,861	4,300	1,840,816
Balance (in shares) at Dec. 31, 2018		476,095,000	53,410,000
Balance at beginning of period at Dec. 31, 2018	2,088,159	$ 47,610	$ (1,334,688)	1,763,142	4,437	1,607,658
Increase (Decrease) in Stockholders' Equity
Net income (loss)	534,130
Balance (in shares) at Sep. 30, 2019		476,882,000	68,957,000
Balance at end of period at Sep. 30, 2019	2,213,576	$ 47,688	$ (1,650,784)	1,775,579	4,027	2,037,066
Balance (in shares) at Mar. 31, 2019		476,777,000	53,410,000
Balance at beginning of period at Mar. 31, 2019	2,320,939	$ 47,678	$ (1,334,716)	1,762,861	4,300	1,840,816
Increase (Decrease) in Stockholders' Equity
Net income (loss)	181,009					181,009
Stock amortization and vesting (in shares)		102,000
Sale of stock held in rabbi trust	6,344	$ 10		6,334
Shares repurchased (in shares)			5,081,000
Purchase of treasury stock	(125,260)		$ (125,260)
Cash dividends	(38,092)					(38,092)
Other comprehensive loss	(136)				(136)
Balance (in shares) at Jun. 30, 2019		476,879,000	58,491,000
Balance at end of period at Jun. 30, 2019	2,344,804	$ 47,688	$ (1,459,976)	1,769,195	4,164	1,983,733
Increase (Decrease) in Stockholders' Equity
Net income (loss)	90,358					90,358
Stock amortization and vesting (in shares)		3,000
Sale of stock held in rabbi trust	6,384			6,384
Shares repurchased (in shares)			10,466,000
Purchase of treasury stock	(190,808)		$ (190,808)
Cash dividends	(37,025)					(37,025)
Other comprehensive loss	(137)				(137)
Balance (in shares) at Sep. 30, 2019		476,882,000	68,957,000
Balance at end of period at Sep. 30, 2019	2,213,576	$ 47,688	$ (1,650,784)	1,775,579	4,027	2,037,066
Balance (in shares) at Dec. 31, 2019		476,882,000	78,957,000
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 (loss)	53,910					53,910
Stock amortization and vesting (in shares)		651,000
Sale of stock held in rabbi trust	2,951	$ 65		2,886
Cash dividends	(39,817)					(39,817)
Other comprehensive loss	(136)				(136)
Balance (in shares) at Mar. 31, 2020		477,533,000	78,957,000
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		476,882,000	78,957,000
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 (loss)	69,323
Balance (in shares) at Sep. 30, 2020		477,537,000	78,957,000
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		477,533,000	78,957,000
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 (loss)	30,374					30,374
Stock amortization and vesting (in shares)		2,000
Sale of stock held in rabbi trust	7,219	$ 1		7,218
Cash dividends	(39,858)					(39,858)
Other comprehensive loss	(151)				(151)
Balance (in shares) at Jun. 30, 2020		477,535,000	78,957,000
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 (loss)	(14,961)					(14,961)
Stock amortization and vesting (in shares)		2,000
Sale of stock held in rabbi trust	7,471			7,471
Cash dividends	(39,857)					(39,857)
Other comprehensive loss	(144)				(144)
Balance (in shares) at Sep. 30, 2020		477,537,000	78,957,000
Balance at end of period at Sep. 30, 2020	$ 2,118,488	$ 47,754	$ (1,823,201)	$ 1,800,002	$ 929	$ 2,093,004