Financial Instruments - Schedule of Changes in Fair Value of Financial Assets and Liabilities Classified as Level 3 (Detail) - Significant Unobservable Inputs (Level 3) [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Assets at beginning of period	$ 2,296
Total realized and unrealized (gains) losses:
Included in earnings	(4,148)	[1]
Purchases, sales, issuances and settlements	1,371
Net Liabilities end of period	$ (481)

[1] Derivative instruments are reported in revenues as realized gain/loss and on a separately reported line item captioned unrealized gain/loss on derivative instruments.