Loans - Variable Rate Loans Held for Investment (Details) $ in Thousands	Mar. 31, 2021 USD ($)
Variable rate loans held-for-investment
Total variable rate loans held-for-investment, carrying value	$ 11,565,002
Weighted average spread of loans (as a percent)	4.20%
Commercial loans
Variable rate loans held-for-investment
Total variable rate loans held-for-investment, carrying value	$ 9,969,387
Weighted average spread of loans (as a percent)	4.30%
Infrastructure loans
Variable rate loans held-for-investment
Total variable rate loans held-for-investment, carrying value	$ 1,595,615
Weighted average spread of loans (as a percent)	3.80%