Debt - Interest expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Cash payments for interest		$ 89,726	$ 112,693	$ 105,086
Amortization of debt issuance costs and other adjustments		3,922	4,243	4,433
Change in accrued interest		(56)	(13,481)	11,804
Interest costs incurred		93,592	103,455	121,323
Less capitalized interest		(294)	(236)	(150)
Total interest expense	[1]	$ 93,298	$ 103,219	$ 121,173

[1] Interest expense was allocated to the exploration and production segment based on gross property and equipment as of December 31, 2016, 2015 and 2014 and allocated to the midstream and marketing segment based on gross property and equipment and life-to-date contributions to the Company's equity method investee as of December 31, 2016, 2015 and 2014.