Fair Value Measurements - Derivative Instrument Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Asset derivative instruments, at fair value	$ 503,648	$ 812,664
Fair value on a recurring basis | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Asset derivative instruments, at fair value	66,840	95,041
Liability derivative instruments, at fair value	131,364	71,107
Fair value on a recurring basis | Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Asset derivative instruments, at fair value	436,808	717,623
Liability derivative instruments, at fair value	763,254	241,589
Fair value on a recurring basis | Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Asset derivative instruments, at fair value	0	0
Liability derivative instruments, at fair value	0	0
Fair value on a recurring basis | Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Asset derivative instruments, at fair value	503,648	812,664
Liability derivative instruments, at fair value	$ 894,618	$ 312,696