Basis of Presentation and Summary of Significant Accounting Policies (Net Earnings (Loss) per Common Share) (Details) - shares shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Weighted average shares for basic EPS	617	616	615	614	615	615	615	613	616	615	617
Dilutive effect of shares issuable under stock-based compensation plans									2	2	4
Weighted average shares for diluted EPS	620	618	617	616	615	617	617	617	618	617	621