Leases - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Dec. 01, 2014	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Capital And Operating Leased Assets [Line Items]
Rental expense			$ 0.6	$ 0.6	$ 0.6
Short-term payment obligations			$ 1.9	$ 4.1
Port Neches Tank Lease
Schedule Of Capital And Operating Leased Assets [Line Items]
Lease agreement effective date			Dec. 01, 2015
Minimum actual and premises operating cost difference percentage required for lease adjustment.	5.00%
Imputed interest rate on capital portion of lease	15.70%
Scenario Forecast | Port Neches Tank Lease
Schedule Of Capital And Operating Leased Assets [Line Items]
Monthly lease payment		$ 0.4