Balance Sheet Accounts - Schedule of Other Noncurrent Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Nov. 30, 2015	Feb. 28, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Conditional asset retirement obligations	$ 29.8	$ 29.5	$ 29.3
Pension benefits, non-qualified	17.5	17.6	17.9
Deferred compensation	12.0	11.5	11.9
Deferred revenue	13.7	13.8	13.9
Competitive improvement program obligations (see Note 9)	2.0	3.2	3.1
Other	19.0	19.6	18.3
Other noncurrent liabilities	$ 94.0	$ 95.2	$ 94.4	$ 81.8