Fair Value Measurements - Valuation of Financial Instruments That are Marked-to-Market on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Estimated Fair Value	$ 2,090,707	$ 487,669
Fair Value Measurements on a Recurring Basis
Assets
Estimated Fair Value	2,090,707	487,669
Derivative instruments	541	715
Total earning assets	2,091,248	488,384
Liabilities
Derivative instruments	0	(1,164)
Fair Value Measurements on a Recurring Basis | Level 1
Assets
Estimated Fair Value	0	0
Derivative instruments	0	0
Total earning assets	0	0
Liabilities
Derivative instruments	0	0
Fair Value Measurements on a Recurring Basis | Level 2
Assets
Estimated Fair Value	2,018,388	487,669
Derivative instruments	541	715
Total earning assets	2,018,929	488,384
Liabilities
Derivative instruments	0	(1,164)
Fair Value Measurements on a Recurring Basis | Level 3
Assets
Estimated Fair Value	72,319	0
Derivative instruments	0	0
Total earning assets	72,319	0
Liabilities
Derivative instruments	$ 0	$ 0