Loans - Variable Rate Loans Held for Investment (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Variable rate loans held-for-investment
Total variable rate loans held-for-investment, carrying value	$ 9,757,786
Weighted average spread of loans (as a percent)	4.10%
Commercial loans
Variable rate loans held-for-investment
Total variable rate loans held-for-investment, carrying value	$ 8,360,382
Weighted average spread of loans (as a percent)	4.20%
Infrastructure loans
Variable rate loans held-for-investment
Total variable rate loans held-for-investment, carrying value	$ 1,397,404
Weighted average spread of loans (as a percent)	3.80%