Fair Value Measurements (Assets and Liabilities Measured on Recurring Basis) (Details) - Recurring - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Assets and liabilities measured at fair value on a recurring basis
Commodity derivatives, net	[1]	$ 428,938	$ 177,467	$ 45,916
Provisionally price contracts	[2]	7,500	(29,025)	(57,036)
Convertible preferred securities	[3]	13,550	8,849	8,654
Other assets and liabilities	[4]	(9,536)	(18,086)	(30,820)
Total		440,452	139,205	(33,286)
Level 1
Assets and liabilities measured at fair value on a recurring basis
Commodity derivatives, net	[1]	38,627	51,369	22,162
Provisionally price contracts	[2]	32,710	19,793	(15,139)
Convertible preferred securities	[3]	0	0	0
Other assets and liabilities	[4]	5,373	7,972	4,102
Total		76,710	79,134	11,125
Level 2
Assets and liabilities measured at fair value on a recurring basis
Commodity derivatives, net	[1]	390,311	126,098	23,754
Provisionally price contracts	[2]	(25,210)	(48,818)	(41,897)
Convertible preferred securities	[3]	0	0	0
Other assets and liabilities	[4]	(14,909)	(26,058)	(34,922)
Total		350,192	51,222	(53,065)
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]	13,550	8,849	8,654
Other assets and liabilities	[4]	0	0	0
Total		$ 13,550	$ 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).