Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income (loss)	$ 314.8	$ 327.0	$ 668.4	$ 696.2
Subtract:
Net income (loss) attributable to noncontrolling interest	5.3	4.7	10.0	5.9
Total	$ 309.5	$ 322.3	$ 658.4	$ 690.3
Weighted-average shares outstanding
Basic	288.9	289.9	288.6	290.7
Dilutive effects:
Diluted	292.7	292.6	292.5	293.4
Net income per common share:
Basic	$ 1.07	$ 1.11	$ 2.28	$ 2.37
Diluted	$ 1.06	$ 1.10	$ 2.25	$ 2.35
Nonqualified Stock Options
Dilutive effects:
Stock-based compensation awards	1.8	1.1	1.8	1.1
Restricted Stock Units
Dilutive effects:
Stock-based compensation awards	1.8	1.4	1.9	1.4
Performance Share Awards
Dilutive effects:
Stock-based compensation awards	0.2	0.2	0.2	0.2