Additional Shareholders' Equity Information - Common Stock and Treasury Stock (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Feb. 15, 2018
Additional Information
Incremental Shares From Assumed Conversion of Dilutive Stock Options, Restricted Stock, and Shares of Common Stock in Rabbi Trust	0	0
Number of Antidilutive Stock Options, Shares of Restricted Stock and Shares of Common Stock in Rabbi Trust excluded from Dilutive Earnings (Loss) per Share (2)	13,892,742	15,004,591
Share repurchase program authorized amount			$ 750,000,000
Repurchase price (in usd per share)		$ 29.49
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance	521,055,001	528,743,381
Exercise of Common Stock Options	0	576,617
Restricted Stock Awarded, Net of Forfeitures	2,768,731	2,488,363
Purchase and Retirement of Common Stock	0	(10,008,128)
Adjustment to Shares Exchanged in Clayton Williams Energy Acquisition	0	(745,232)
Shares, ending balance	523,823,732	521,055,001
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance	38,851,988	38,786,969
Shares Received in Payment of Withholding Taxes Due on Vesting of Shares of Restricted Stock	240,865	267,258
Rabbi Trust Shares Distributed and/or Sold	(203,063)	(202,239)
Shares, ending balance	38,889,790	38,851,988