Goodwill and Other Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Jan. 03, 2018
Goodwill [Line Items]
Goodwill	$ 796,359,000			$ 796,359,000		$ 796,359,000
Impairment of intangible asset	0	$ 0		0	$ 18,650,000
Amortization expense	1,638,000	$ 1,638,000		$ 4,915,000	5,293,000
Useful life, customer relationship intangible assets				17 years
Estimated annual amortization expense	6,552,000			$ 6,552,000
Midstream Acquisition
Goodwill [Line Items]
Goodwill							$ 796,359,000
Other intangible assets							$ 128,781,000
Customer Relationships
Goodwill [Line Items]
Impairment of intangible asset					$ 18,650,000
Customer Relationships | Midstream Acquisition
Goodwill [Line Items]
Impairment of intangible asset	$ 0		$ 18,650,000