Revenue - Minimum Volume Commitments (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 1,482,892
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 24,351
Expected timing of satisfaction period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 324,289
Expected timing of satisfaction period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 159,160
Expected timing of satisfaction period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 158,725
Expected timing of satisfaction period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 158,725
Expected timing of satisfaction period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 158,725
Expected timing of satisfaction period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 498,917
Expected timing of satisfaction period
Gathering And Compression Agreement
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 1,317,328
Gathering And Compression Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 24,351
Expected timing of satisfaction period	3 months
Gathering And Compression Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 158,725
Expected timing of satisfaction period	12 months
Gathering And Compression Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 159,160
Expected timing of satisfaction period	12 months
Gathering And Compression Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 158,725
Expected timing of satisfaction period	12 months
Gathering And Compression Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 158,725
Expected timing of satisfaction period	12 months
Gathering And Compression Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 158,725
Expected timing of satisfaction period	12 months
Gathering And Compression Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 498,917
Expected timing of satisfaction period
Water Services Agreement
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 165,564
Water Services Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Minimum revenue amounts under the minimum volume commitments
Minimum revenue amounts	$ 165,564
Expected timing of satisfaction period	12 months