Statements of Condensed Consolidated Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands		Total		Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Treasury Stock	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjustment
Comprehensive income (loss), net of tax
Change in accounting principle	[1]			$ 0				$ 496		$ (496)
Beginning balance (in shares) at Dec. 31, 2018					254,472
Beginning balance at Dec. 31, 2018		$ 10,958,229			$ 7,828,554	$ (49,194)	$ 3,184,275		$ (5,406)
Comprehensive income (loss), net of tax
Net loss		(44,771)					(44,771)
Net change in interest rate cash flow hedges, net of tax expense		127	[2]						127
Other post-retirement benefit liability adjustment, net of tax expense		229	[3]						229
Dividends		(22,985)					(22,985)
Share-based compensation plans (in shares)					920
Share-based compensation plans		21,266			$ 4,599	16,667
Other (in shares)					(222)
Other		(14,470)			$ (14,470)
Ending balance (in shares) at Sep. 30, 2019					255,170
Ending balance at Sep. 30, 2019		10,897,625			$ 7,818,683	(32,527)	3,117,015		(5,546)
Beginning balance (in shares) at Jun. 30, 2019					254,796
Beginning balance at Jun. 30, 2019		11,248,475			$ 7,807,740	(39,310)	3,485,711		(5,666)
Comprehensive income (loss), net of tax
Net loss		(361,028)					(361,028)
Net change in interest rate cash flow hedges, net of tax expense		43	[2]						43
Other post-retirement benefit liability adjustment, net of tax expense		77	[3]						77
Dividends		(7,668)					(7,668)
Share-based compensation plans (in shares)					374
Share-based compensation plans		17,726			$ 10,943	6,783
Ending balance (in shares) at Sep. 30, 2019					255,170
Ending balance at Sep. 30, 2019		10,897,625			$ 7,818,683	(32,527)	3,117,015		(5,546)
Beginning balance (in shares) at Dec. 31, 2019					255,171
Beginning balance at Dec. 31, 2019		9,803,588			$ 7,818,205	(32,507)	2,023,089		(5,199)
Comprehensive income (loss), net of tax
Net loss		(1,030,854)					(1,030,854)
Net change in interest rate cash flow hedges, net of tax expense	[2]	0
Other post-retirement benefit liability adjustment, net of tax expense		156	[3]						156
Dividends		(7,664)					(7,664)
Share-based compensation plans (in shares)					174
Share-based compensation plans		16,938			$ 13,778	3,160
Equity component of convertible senior notes (See Note 6)		63,645			$ 63,645
Ending balance (in shares) at Sep. 30, 2020					255,345
Ending balance at Sep. 30, 2020		8,845,809			$ 7,895,628	(29,347)	984,571		(5,043)
Beginning balance (in shares) at Jun. 30, 2020					255,290
Beginning balance at Jun. 30, 2020		9,438,827			$ 7,889,072	(30,341)	1,585,211		(5,115)
Comprehensive income (loss), net of tax
Net loss		(600,640)					(600,640)
Net change in interest rate cash flow hedges, net of tax expense	[2]	0
Other post-retirement benefit liability adjustment, net of tax expense		72	[3]						72
Share-based compensation plans (in shares)					55
Share-based compensation plans		7,550			$ 6,556	994
Equity component of convertible senior notes (See Note 6)		63,600
Ending balance (in shares) at Sep. 30, 2020					255,345
Ending balance at Sep. 30, 2020		$ 8,845,809			$ 7,895,628	$ (29,347)	$ 984,571		$ (5,043)

[1] Related to adoption of ASU 2018-02.

[2] Net of tax expense of $10 and $30 for the three and nine months ended September 30, 2019.

[3] Net of tax expense of $23 and $26 for the three months ended September 30, 2020 and 2019, respectively, and $71 and $78 for the nine months ended September 30, 2020 and 2019, respectively.