Investment Securities - HTM Debt Securities, Amortized Cost​ (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
HTM Securities
Amortized Cost Basis	$ 619,397	$ 676,652
Credit Loss Allowance	(13,143)	(3,182)	$ (8,610)
Net Carrying Amount	606,254	673,470
Gross Unrealized Holding Gains	75	202
Gross Unrealized Holding Losses	(25,169)	(36,397)
Fair Value	581,160	637,275
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at beginning	3,182	8,610	5,675
Credit loss provision (reversal), net	9,961	(5,428)	2,935
Credit loss allowance at ending	13,143	3,182	8,610
HTM preferred equity interests
Less than one year	96,548
One to three years	444,175
Three to five years	56,417
Thereafter	9,114
Total	606,254
CMBS
HTM Securities
Amortized Cost Basis	580,704	577,681
Credit Loss Allowance	(164)	(172)	(3,140)
Net Carrying Amount	580,540	577,509
Gross Unrealized Holding Gains	43	30
Gross Unrealized Holding Losses	(24,835)	(30,424)
Fair Value	555,748	547,115
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at beginning	172	3,140	0
Credit loss provision (reversal), net	(8)	(2,968)	3,140
Credit loss allowance at ending	164	172	3,140
HTM preferred equity interests
Less than one year	96,548
One to three years	437,173
Three to five years	46,819
Thereafter	0
Total	580,540
Preferred interests
HTM Securities
Amortized Cost Basis	9,570	29,757
Credit Loss Allowance	(2,898)	0	(2,562)
Net Carrying Amount	6,672	29,757
Gross Unrealized Holding Gains	0	125
Gross Unrealized Holding Losses	(318)	(4,863)
Fair Value	6,354	25,019
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at beginning	0	2,562	2,749
Credit loss provision (reversal), net	2,898	(2,562)	(187)
Credit loss allowance at ending	2,898	0	2,562
HTM preferred equity interests
Less than one year	0
One to three years	6,672
Three to five years	0
Thereafter	0
Total	6,672
Infrastructure bonds
HTM Securities
Amortized Cost Basis	29,123	69,214
Credit Loss Allowance	(10,081)	(3,010)	(2,908)
Net Carrying Amount	19,042	66,204
Gross Unrealized Holding Gains	32	47
Gross Unrealized Holding Losses	(16)	(1,110)
Fair Value	19,058	65,141
Activity in credit loss allowance for HTM debt securities
Credit loss allowance at beginning	3,010	2,908	2,926
Credit loss provision (reversal), net	7,071	102	(18)
Credit loss allowance at ending	10,081	$ 3,010	$ 2,908
HTM preferred equity interests
Less than one year	0
One to three years	330
Three to five years	9,598
Thereafter	9,114
Total	$ 19,042