Long-Term Debt - Additional Information (Details)		3 Months Ended
	May 11, 2017 USD ($) Bank	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2017
Debt Instrument [Line Items]
Credit facility syndication, number of commercial banks | Bank	11
Line of credit facility, expiration date		May 17, 2022
Line of credit facility, maximum borrowing capacity without borrowing base requirement	$ 600,000,000
Line of credit facility, accordion feature, additional revolving credit commitments under existing loan facility	300,000,000
Line of credit facility, maximum borrowing capacity	$ 60,000,000
Line of credit facility, interest coverage ratio covenant	300.00%
Line of credit facility, leverage ratio covenant	375.00%
Long-term debt		$ 231,490,000	$ 206,250,000
Number of letters of credit, outstanding		12
Letters of credit outstanding, amount		$ 3,600,000
Line of credit facility, remaining borrowing capacity		364,900,000
Line of credit facility, current borrowing capacity		$ 264,900,000
Long-term debt, weighted average interest rate, at point in time		2.80%		2.60%
Minimum
Debt Instrument [Line Items]
Line of Credit Facility, Committement Fee Unused Capacity	0.13%
Maximum
Debt Instrument [Line Items]
Line of Credit Facility, Committement Fee Unused Capacity	0.25%
Federal Funds Open Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.50%
London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.00%
London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%