Supplemental Information (Earnings Per Share) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share Reconciliation [Abstract]
Average Common Shares Outstanding - Basic (in shares)	245,900,000	244,100,000	245,500,000	243,600,000
Assumed settlement of performance share units and restricted stock units (in shares)	1,400,000	2,200,000	1,400,000	1,900,000
Dilutive effect of forward sale agreement (in shares)	200,000	0	100,000	0
Weighted Average Number of Shares Outstanding, Diluted (in shares)	247,500,000	246,300,000	247,000,000.0	245,500,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	0	0	0	0