Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	At-the-market Offering [Member] Preferred Stock Outstanding [Member]	At-the-market Offering [Member] Common Stock Outstanding [Member]	At-the-market Offering [Member] Additional Paid-in Capital [Member]	At-the-market Offering [Member] Retained Earnings [Member]	At-the-market Offering [Member] Treasury Stock, Common [Member]	At-the-market Offering [Member] Treasury Stock, Preferred [Member]	At-the-market Offering [Member] Noncontrolling Interest [Member] Variable Interest Entity, Primary Beneficiary [Member]	At-the-market Offering [Member] Noncontrolling Interest [Member] Subsidiaries [Member]	At-the-market Offering [Member]	Public Offering [Member] Preferred Stock Outstanding [Member]	Public Offering [Member] Common Stock Outstanding [Member]	Public Offering [Member] Additional Paid-in Capital [Member]	Public Offering [Member] Retained Earnings [Member]	Public Offering [Member] Treasury Stock, Common [Member]	Public Offering [Member] Treasury Stock, Preferred [Member]	Public Offering [Member] Noncontrolling Interest [Member] Variable Interest Entity, Primary Beneficiary [Member]	Public Offering [Member] Noncontrolling Interest [Member] Subsidiaries [Member]	Public Offering [Member]	Private Placement [Member] Preferred Stock Outstanding [Member]	Private Placement [Member] Common Stock Outstanding [Member]	Private Placement [Member] Additional Paid-in Capital [Member]	Private Placement [Member] Retained Earnings [Member]	Private Placement [Member] Treasury Stock, Common [Member]	Private Placement [Member] Treasury Stock, Preferred [Member]	Private Placement [Member] Noncontrolling Interest [Member] Variable Interest Entity, Primary Beneficiary [Member]	Private Placement [Member] Noncontrolling Interest [Member] Subsidiaries [Member]	Private Placement [Member]	Preferred Stock Outstanding [Member]	Common Stock Outstanding [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock, Common [Member]	Treasury Stock, Preferred [Member]	Noncontrolling Interest [Member] Variable Interest Entity, Primary Beneficiary [Member]	Noncontrolling Interest [Member] Subsidiaries [Member]	Total
Balances (in shares) at Dec. 31, 2019																												0	0
Balances at Dec. 31, 2019																												$ 0	$ 0	$ 0	$ 0	$ 0	$ 0			$ 0
Vesting of stock-based compensation																												$ 0	$ 0	292	0	0	0			292
Issuance of common shares (in shares)																													5,350,000
Issuance of common shares																													$ 54	91,434	0	0	0			91,488
Net income attributable to preferred stockholders																												0	0	0	874	0	0			874
Net income attributable to common stockholders																												0	0	0	1,779	0	0			1,779
Preferred stock dividends declared																												0	0	0	(874)	0	0			(874)
Common stock dividends declared																												$ 0	$ 0	0	(5,488)	0	0			(5,488)
Issuance of preferred stock through public offering, net (in shares)																												2,000,000	0
Issuance of preferred stock through public offering, net																												$ 20	$ 0	46,061	0	0	0			46,081
Repurchase of common stock (in shares)																												0	(113,511)
Repurchase of common stock																												$ 0	$ (1)	0	0	(1,715)	0			(1,716)
Repurchase of preferred stock (in shares)																												(355,000)	0
Repurchase of preferred stock																												$ (4)	$ 0	0	0	0	(8,567)			(8,571)
Balances (in shares) at Sep. 30, 2020																												1,645,000	5,236,489
Balances at Sep. 30, 2020																												$ 16	$ 53	137,787	(3,709)	(1,715)	(8,567)			123,865
Balances (in shares) at Jun. 30, 2020																												0	5,262,534
Balances at Jun. 30, 2020																												$ 0	$ 53	91,933	(4,351)	(1,338)	0			86,297
Vesting of stock-based compensation																												$ 0	$ 0	252	0	0	0			252
Issuance of common shares (in shares)																												0	0
Net income attributable to preferred stockholders																												$ 0	$ 0	0	874	0	0			874
Net income attributable to common stockholders																												0	0	0	2,862	0	0			2,862
Preferred stock dividends declared																												0	0	0	(874)	0	0			(874)
Common stock dividends declared																												0	0	0	(2,220)	0	0			(2,220)
Issuance of common stock through public offering, net																												$ 0	$ 0	(459)	0	0	0			(459)
Issuance of preferred stock through public offering, net (in shares)																												2,000,000	0
Issuance of preferred stock through public offering, net																												$ 20	$ 0	46,061	0	0	0			46,081
Repurchase of common stock (in shares)																												0	(26,045)
Repurchase of common stock																												$ 0	$ 0	0	0	(377)	0			(377)
Repurchase of preferred stock (in shares)																												(355,000)	0
Repurchase of preferred stock																												$ (4)	$ 0	0	0	0	(8,567)			(8,571)
Balances (in shares) at Sep. 30, 2020																												1,645,000	5,236,489
Balances at Sep. 30, 2020																												$ 16	$ 53	137,787	(3,709)	(1,715)	(8,567)			123,865
Balances (in shares) at Dec. 31, 2020																												1,645,000	5,022,578
Balances at Dec. 31, 2020																												$ 16	$ 50	138,043	3,485	(4,784)	(8,567)	$ 0	$ 0	128,243
Balances (in shares) at Jun. 30, 2021																												1,645,000	5,498,980
Balances at Jun. 30, 2021																												$ 16	$ 55	145,786	11,964	(4,195)	(8,567)	6,869	98	152,026
Balances (in shares) at Dec. 31, 2020																												1,645,000	5,022,578
Balances at Dec. 31, 2020																												$ 16	$ 50	138,043	3,485	(4,784)	(8,567)	0	0	128,243
Vesting of stock-based compensation (in shares)																												0	67,992
Vesting of stock-based compensation																												$ 0	$ 1	1,166	0	0	0	0	0	1,167
Issuance of common shares (in shares)	0	532,694							532,694	0	2,059,700
Issuance of common shares	$ 0	$ 5	$ 10,397	$ 0	$ 0	$ 0	$ 0	$ 0	$ 10,402	$ 0	$ 21	$ 40,962	$ 0	$ 0	$ 0	$ 0		$ 40,983
Conversion of redeemable noncontrolling interests in the OP (in shares)																												0	1,479,132
Conversion of redeemable noncontrolling interests in the OP																												$ 0	$ 15	32,378	0	0	0	0	0	32,393
Noncontrolling interest in CMBS VIEs																												0	0	0	0	0	0	7,069	0	7,069
Net income attributable to preferred stockholders																												0	0	0	2,626	0	0	0	0	2,626
Net income attributable to common stockholders																												0	0	0	27,142	0	0	0	0	27,142
Preferred stock dividends declared																												0	0	0	(2,626)	0	0	0	0	(2,626)
Common stock dividends declared																												0	0	0	(9,991)	0	0	0	0	(9,991)
Cancellation of common stock held in treasury																												$ 0	$ 0	(589)	0	589	0	0	0	0
Issuance of subsidiary preferred membership units through private offering, net																			$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 95	$ 95
Balances (in shares) at Sep. 30, 2021																												1,645,000	9,162,096
Balances at Sep. 30, 2021																												$ 16	$ 92	222,357	20,636	(4,195)	(8,567)	7,069	95	237,503
Balances (in shares) at Jun. 30, 2021																												1,645,000	5,498,980
Balances at Jun. 30, 2021																												$ 16	$ 55	145,786	11,964	(4,195)	(8,567)	6,869	98	152,026
Vesting of stock-based compensation (in shares)																												0	0
Vesting of stock-based compensation																												$ 0	$ 0	538	0	0	0	0	0	538
Issuance of common shares (in shares)	0	124,284								0	2,059,700
Issuance of common shares	$ 0	$ 1	$ 2,693	$ 0	$ 0	$ 0	$ 0	$ 0	$ 2,694	$ 0	$ 21	$ 40,962	$ 0	$ 0	$ 0	$ 0	$ 0	$ 40,983
Issuance of subsidiary preferred membership units through private offering, net																			$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ (3)	$ (3)
Conversion of redeemable noncontrolling interests in the OP (in shares)																												0	1,479,132
Conversion of redeemable noncontrolling interests in the OP																												$ 0	$ 15	32,378	0	0	0	0	0	32,393
Noncontrolling interest in CMBS VIEs																												0	0	0	0	0	0	200	0	200
Net income attributable to preferred stockholders																												0	0	0	874	0	0	0	0	874
Net income attributable to common stockholders																												0	0	0	13,233	0	0	0	0	13,233
Preferred stock dividends declared																												0	0	0	(874)	0	0	0	0	(874)
Common stock dividends declared																												$ 0	$ 0	0	(4,561)	0	0	0	0	(4,561)
Balances (in shares) at Sep. 30, 2021																												1,645,000	9,162,096
Balances at Sep. 30, 2021																												$ 16	$ 92	$ 222,357	$ 20,636	$ (4,195)	$ (8,567)	$ 7,069	$ 95	$ 237,503