CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Treasury stock	Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance (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	262,763					262,763
Stock amortization and vesting (shares)		682,000
Sale of stock held in rabbi trust	(213)	$ 68		(281)
Purchase of treasury stock (shares)			0
Purchase of treasury stock	(28)		$ (28)
Cash dividends	(29,605)					(29,605)
Other comprehensive loss	(137)				(137)
Balance (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 (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	443,772
Balance (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
Balance (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	181,009					181,009
Stock amortization and vesting (shares)		102,000
Sale of stock held in rabbi trust	6,344	$ 10		6,334
Purchase of treasury stock (shares)			5,081,000
Purchase of treasury stock	(125,260)		$ (125,260)
Cash dividends	(38,092)					(38,092)
Other comprehensive loss	(136)				(136)
Balance (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
Balance (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	53,910					53,910
Stock amortization and vesting (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 (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 (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	84,284
Balance (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
Balance (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	30,374					30,374
Stock amortization and vesting (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 (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