Investment Securities - HTM (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
HTM Securities
Amortized Cost Basis	$ 493,123	$ 544,280
Credit Loss Allowance	(6,389)	(5,675)
Net Carrying Amount	486,734	538,605
Gross Unrealized Holding Gains	3,913	847
Gross Unrealized Holding Losses	(23,490)	(24,199)
Fair Value	467,157	515,253
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at December 31, 2020	5,675
Credit loss provision (reversal), net	714
Credit loss allowance at September 30, 2021	6,389
HTM preferred equity interests
Less than one year	313,928
One to three years	139,484
Three to five years	814
Thereafter	32,508
Total	486,734
CMBS
HTM Securities
Amortized Cost Basis	339,190	339,059
Credit Loss Allowance	(1,593)	0
Net Carrying Amount	337,597	339,059
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	(23,490)	(23,286)
Fair Value	314,107	315,773
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at December 31, 2020	0
Credit loss provision (reversal), net	1,593
Credit loss allowance at September 30, 2021	1,593
HTM preferred equity interests
Less than one year	313,928
One to three years	23,669
Three to five years	0
Thereafter	0
Total	337,597
Preferred interests
HTM Securities
Amortized Cost Basis	117,692	166,614
Credit Loss Allowance	(1,877)	(2,749)
Net Carrying Amount	115,815	163,865
Gross Unrealized Holding Gains	3,415	432
Gross Unrealized Holding Losses	0	(913)
Fair Value	119,230	163,384
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at December 31, 2020	2,749
Credit loss provision (reversal), net	(872)
Credit loss allowance at September 30, 2021	1,877
HTM preferred equity interests
Less than one year	0
One to three years	115,815
Three to five years	0
Thereafter	0
Total	115,815
Infrastructure bonds
HTM Securities
Amortized Cost Basis	36,241	38,607
Credit Loss Allowance	(2,919)	(2,926)
Net Carrying Amount	33,322	35,681
Gross Unrealized Holding Gains	498	415
Gross Unrealized Holding Losses	0	0
Fair Value	33,820	$ 36,096
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at December 31, 2020	2,926
Credit loss provision (reversal), net	(7)
Credit loss allowance at September 30, 2021	2,919
HTM preferred equity interests
Less than one year	0
One to three years	0
Three to five years	814
Thereafter	32,508
Total	$ 33,322