Fair Value Measurements (Assets and Liabilities Measured on Recurring Basis) (Details) - Recurring - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Assets and liabilities measured at fair value on a recurring basis
Commodity derivatives, net	[1]	$ 231,315	$ 177,467	$ 59,175
Provisionally price contracts	[2]	(17,371)	(29,025)	(145,895)
Convertible preferred securities	[3]	11,649	8,849	8,654
Other assets and liabilities	[4]	(6,627)	(18,086)	(27,241)
Total		218,966	139,205	(105,307)
Level 1
Assets and liabilities measured at fair value on a recurring basis
Commodity derivatives, net	[1]	19,145	51,369	43,832
Provisionally price contracts	[2]	14,231	19,793	(94,834)
Convertible preferred securities	[3]	0	0	0
Other assets and liabilities	[4]	6,147	7,972	5,373
Total		39,523	79,134	(45,629)
Level 2
Assets and liabilities measured at fair value on a recurring basis
Commodity derivatives, net	[1]	212,170	126,098	15,343
Provisionally price contracts	[2]	(31,602)	(48,818)	(51,061)
Convertible preferred securities	[3]	0	0	0
Other assets and liabilities	[4]	(12,774)	(26,058)	(32,614)
Total		167,794	51,222	(68,332)
Level 3
Assets and liabilities measured at fair value on a recurring basis
Commodity derivatives, net	[1]	0	0	0
Provisionally price contracts	[2]	0	0	0
Convertible preferred securities	[3]	11,649	8,849	8,654
Other assets and liabilities	[4]	0	0	0
Total		$ 11,649	$ 8,849	$ 8,654

[1] Includes associated cash posted/received as collateral

[2] Included in "Provisionally priced contracts" are those instruments based only on underlying futures values (Level 1) and delayed price contracts (Level 2)

[3] Recorded in “Other assets, net” on the Company’s Consolidated Balance Sheets related to certain available for sale securities.

[4] Included in other assets and liabilities are assets held by the Company to fund deferred compensation plans and foreign exchange derivative contracts (Level 1), as well as, interest rate derivatives (Level 2).