Supplemental Information (Earnings Per Share) (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share Reconciliation [Abstract]
Weighted-average Common Shares Outstanding – Basic	256,100,000	246,900,000	255,200,000	246,700,000
Assumed settlement of performance share units and restricted stock units	1,100,000	1,000,000.0	1,300,000	1,000,000.0
Dilutive effect of forward sale agreement	0	0	0	300,000
Weighted-average Common Shares Outstanding – Diluted	257,200,000	247,900,000	256,500,000	248,000,000.0
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	0	0	0	0