Balance Sheet Accounts - Schedule of Other Noncurrent Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Conditional asset retirement obligations	$ 40.3	$ 30.6
Pension benefits, non-qualified	17.1	17.5
Deferred compensation	31.1	19.8
Deferred revenue	12.8	13.3
Competitive improvement program obligations (see Note 10)	22.9	1.3
Uncertain income tax positions	24.4	28.4
Other	13.4	13.1
Other noncurrent liabilities	$ 162.0	$ 124.0