Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net income (loss)	$ 392.1	$ 459.5	$ 844.2	$ 862.0
Subtract:
Net income (loss) attributable to noncontrolling interest	5.8	2.9	28.0	8.3
Total	$ 386.3	$ 456.6	$ 816.2	$ 853.7
Weighted-average shares outstanding:
Basic	279.0	286.4	278.8	287.9
Dilutive effects:
Diluted	281.2	289.2	281.2	291.1
Net income (loss) per common share:
Basic	$ 1.38	$ 1.59	$ 2.93	$ 2.97
Diluted	$ 1.37	$ 1.58	$ 2.90	$ 2.93
Nonqualified Stock Options
Dilutive effects:
Stock-based compensation awards	0.9	1.0	0.9	1.2
Restricted Stock Units
Dilutive effects:
Stock-based compensation awards	1.2	1.6	1.3	1.8
Performance Share Awards
Dilutive effects:
Stock-based compensation awards	0.1	0.2	0.2	0.2