Acquisitions (Schedule of Consideration Paid to Equity Holders of GEPH) (Details) - GEPH Merger $ / shares in Units, $ in Millions	Dec. 31, 2021 USD ($) $ / shares shares
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Shares of Southwestern common stock issued (in shares) | shares	99,337,748
NYSE closing price per share of Southwestern common shares (in dollars per share) | $ / shares	$ 4.66
Value of Southwestern's stock issued as consideration	$ 463
Cash consideration including post-close adjustments	1,263
Total consideration	1,726
Customary post-close cash consideration, adjustment	$ (6)