Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash paid during the year
Interest—net of interest capitalized	$ 144.0	$ 100.0	$ 141.0
Income taxes—net of refunds	(110.0)	435.0	781.0
Supplemental disclosure of noncash investing and financing activities:
Change in capitalized expenditures in accounts payable and accrued expenses	(263.0)	258.0	72.0
Change in capitalized expenditures in other liabilities	(55.0)	6.0	(22.0)
Change in noncontrolling interests in other liabilities	8.0	0.0	0.0
Change in accrued share repurchases	$ 0.0	$ (29.0)	$ (11.0)