Sales/Exchanges of Assets (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 28, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Pre-tax gain recorded		$ 0	$ 8,025	$ 0
Non-core Marcellus Gathering System
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of oil and gas property and equipment	$ 75,000
Pre-tax gain recorded	$ 8,000