Fair Value Measurements - Summary of Assets and Liabilities Carried at Book Value (Details) - USD ($) $ in Thousands		Dec. 31, 2017		Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book value		$ 380,569		$ 198,682
Senior Notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book value	[1]	245,088		0
Senior Notes due 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book value	[2]	0		175,991
Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book value		100,000	[1]	0	[2]
Portion at Other than Fair Value Measurement | Senior Notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		243,913
Portion at Other than Fair Value Measurement | Senior Notes due 2024 | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		0
Portion at Other than Fair Value Measurement | Senior Notes due 2024 | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		243,913
Portion at Other than Fair Value Measurement | Senior Notes due 2024 | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		0
Portion at Other than Fair Value Measurement | Senior Notes due 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[3]			184,373
Portion at Other than Fair Value Measurement | Senior Notes due 2021 | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[3]			0
Portion at Other than Fair Value Measurement | Senior Notes due 2021 | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[3]			184,373
Portion at Other than Fair Value Measurement | Senior Notes due 2021 | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[3]			$ 0
Portion at Other than Fair Value Measurement | Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		100,000
Portion at Other than Fair Value Measurement | Revolving Credit Facility | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		0
Portion at Other than Fair Value Measurement | Revolving Credit Facility | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		100,000
Portion at Other than Fair Value Measurement | Revolving Credit Facility | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		$ 0

[1] Net of unamortized debt issuance costs of $4.9 million at December 31, 2017.

[2] Net of unamortized debt issuance costs and premium received of $2.0 million at December 31, 2016.

[3] Net of unamortized debt issuance costs and premium received of $2.0 million.