Debt (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	May 19, 2016 USD ($)
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 0		$ 0
Amortization of debt issuance costs	300	$ 200	872	$ 498
Unamortized debt issue costs	800		800		$ 1,400
Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity	282,000		282,000
Credit agreement available	48,000		48,000
Sub-limit which may be used for issuance of letters of credit	15,000		$ 15,000
Borrowing base amount						$ 200,000
Commitment fee on unutilized borrowing base			0.50%
Credit agreement, outstanding	$ 162,000		$ 162,000
Credit Agreement | Thereafter
Line of Credit Facility [Line Items]
Debt to Adjusted EBITDA ratio	4.5		4.5
Credit Facility Maturing March 31, 2020
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 500,000		$ 500,000
Lender loan
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 210,000		$ 210,000
Minimum | Credit Agreement
Line of Credit Facility [Line Items]
Consolidated current asset ratio			1.0
Required interest coverage ratio			2.5
Distribution limitation, credit facility excess over borrowing base (as a percent)			90.00%
Ownership percentage by subsidiary			50
Minimum | Credit Agreement | Scenario One
Line of Credit Facility [Line Items]
Debt to Adjusted EBITDA ratio	4.5		4.5
Minimum | Credit Agreement | Scenario Two
Line of Credit Facility [Line Items]
Debt to Adjusted EBITDA ratio	4.0		4.0
Minimum | Credit Agreement | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Variable interest rate			2.25%
Minimum | Credit Agreement | ABR
Line of Credit Facility [Line Items]
Variable interest rate			1.25%
Maximum | Credit Agreement | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Variable interest rate			3.25%
Maximum | Credit Agreement | ABR
Line of Credit Facility [Line Items]
Variable interest rate			2.25%