Change in Method of Accounting for NRP's Warrants Narrative (Details) - USD ($) $ in Thousands, shares in Millions		3 Months Ended		6 Months Ended
	Mar. 02, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017
Class of Stock [Line Items]
Other Nonoperating Income (Expense)		$ 24,000	$ 16,600	$ 40,500
Warrant issuance expense			0	$ 0
Warrant Holders
Class of Stock [Line Items]
Class of Warrant or Right, Warrants Issued	4.0
Warrant holders interest, net	$ 78,000
Warrant issuance expense			$ 5,700