Fair Value Measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 15,550
Derivatives asset, Fair Value	32
Derivative liability, notional	2,303,126	$ 5,229,373
Derivative liability, Fair Value	786	1,414
To Be Announced Security [Member] | Other Contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	15,550
Derivatives asset, Fair Value	32
Derivative liability, notional	15,550	13,245
Derivative liability, Fair Value	40	124
Future [Member] | Commodity Contracts
Derivatives, Fair Value [Line Items]
Derivative liability, notional	2,285,000	5,209,000	[1]
Derivative liability, Fair Value	397	267	[1]
Foreign exchange forward contracts | Other Contracts
Derivatives, Fair Value [Line Items]
Derivative liability, notional	200
Derivative liability, Fair Value	17
Auction Rate Securities Purchase Commitment | Other Contracts
Derivatives, Fair Value [Line Items]
Derivative liability, notional	2,376	7,128
Derivative liability, Fair Value	$ 332	$ 1,023

[1] For both the three and six months ended June 30, 2020, the diluted earnings per share computation does not include the anti-dilutive effect of 10,770 shares of Class A Stock granted under share-based compensation arrangements (7,628 shares for both the three and six months ended June 30, 2019).