Balance Sheet Accounts and Supplemental Disclosures - Other Noncurrent Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Conditional asset retirement obligations	$ 30.6	$ 29.5
Pension benefits, non-qualified	17.5	17.6
Deferred compensation	19.8	11.5
Deferred revenue	13.3	13.8
Competitive improvement program obligations (see Note 10)	1.3	3.2
Liability for Uncertainty in Income Taxes, Noncurrent	28.4	7.0
Other	13.1	12.6
Other noncurrent liabilities	$ 124.0	$ 95.2