Other Information (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Natural gas and NGLs inventory	$ 59.1	$ 17.4
Prepaid expenses and other	14.3	16.1
Natural gas and NGLs inventory, prepaid expenses and other	73.4	33.5
Accrued interest	64.8	34.2
Accrued wages and benefits, including taxes	23.2	19.0
Accrued ad valorem taxes	33.5	23.5
Capital expenditure accruals	43.6	64.6
Onerous performance obligations	15.4	15.9
Other	54.7	60.3
Other current liabilities	$ 235.2	$ 217.5