Accrued Liabilities - Third Parties (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Transportation, project engineering	$ 3.5	$ 3.0
Property taxes	0.6	0.3
FERC accrual	0.0	1.7
Professional fees	0.3	1.2
Other accrued liabilities	1.2	0.6
Accrued liabilities - third parties	$ 5.6	$ 6.8