Segment Data - Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Assets:
Cash and cash equivalents	$ 195,319		$ 261,061
Restricted cash	235,951		121,072
Loans held-for-investment, net	17,234,205		18,401,439
Loans held-for-sale	2,602,265		2,784,594
Investment securities	721,593		815,804
Properties, net	1,405,791		1,449,986
Investments in unconsolidated entities	91,924		91,892
Goodwill	259,846		259,846
Intangible assets	65,989		68,773
Derivative assets	133,016		108,621
Accrued interest receivable	173,260		168,521
Other assets	526,442		297,477
VIE assets, at fair value	44,668,904		52,453,041
Total Assets	70,293,689		79,043,129
Liabilities:
Dividends payable	152,737		151,511
Derivative liabilities	85,657		91,404
Secured financing agreements, net	13,557,881		14,501,532
Collateralized loan obligations and single asset securitization, net	3,518,274		3,676,224
Unsecured senior notes, net	2,456,583		2,329,211
VIE liabilities, at fair value	42,997,104		50,754,355
Total Liabilities	63,200,233		71,844,422
Temporary Equity: Redeemable non-controlling interests	409,659		362,790
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	3,205		3,181
Additional paid-in capital	5,855,962		5,807,087
Treasury stock	(138,022)		(138,022)
Retained earnings (accumulated deficit)	585,756		769,237
Accumulated other comprehensive income	14,114		20,955
Total Starwood Property Trust, Inc. Stockholders’ Equity	6,321,015		6,462,438
Non-controlling interests in consolidated subsidiaries	362,782		373,479
Total Permanent Equity	6,683,797	$ 6,784,943	6,835,917	$ 6,821,185	$ 6,774,387	$ 6,433,892
Total Liabilities and Equity	70,293,689		79,043,129
Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	407,715		298,999
Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	24,282		41,186
Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	1,979,184		1,761,002
Total Assets	74,800
Liabilities:
Total Liabilities	34,800
Infrastructure Lending Segment
Assets:
Goodwill	119,400		119,400
Investing and Servicing Segment
Assets:
Goodwill	140,400		140,400
Subtotal
Assets:
Cash and cash equivalents	195,319		261,061
Restricted cash	235,951		121,072
Loans held-for-investment, net	17,234,205		18,401,439
Loans held-for-sale	2,602,265		2,784,594
Investment securities	2,363,380		2,482,725
Properties, net	1,405,791		1,449,986
Investments in unconsolidated entities	106,481		105,434
Goodwill	259,846		259,846
Intangible assets	101,963		107,831
Derivative assets	133,016		108,621
Accrued interest receivable	173,545		168,796
Other assets	526,442		297,477
VIE assets, at fair value	0		0
Total Assets	27,317,388		28,309,884
Liabilities:
Dividends payable	152,737		151,511
Derivative liabilities	85,657		91,404
Secured financing agreements, net	13,578,739		14,522,698
Collateralized loan obligations and single asset securitization, net	3,518,274		3,676,224
Unsecured senior notes, net	2,456,583		2,329,211
VIE liabilities, at fair value	0		0
Total Liabilities	20,223,987		21,111,233
Temporary Equity: Redeemable non-controlling interests	409,659		362,790
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	3,205		3,181
Additional paid-in capital	5,855,962		5,807,087
Treasury stock	(138,022)		(138,022)
Retained earnings (accumulated deficit)	585,756		769,237
Accumulated other comprehensive income	14,114		20,955
Total Starwood Property Trust, Inc. Stockholders’ Equity	6,321,015		6,462,438
Non-controlling interests in consolidated subsidiaries	362,727		373,423
Total Permanent Equity	6,683,742		6,835,861
Total Liabilities and Equity	27,317,388		28,309,884
Subtotal | Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	407,715		298,999
Subtotal | Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	24,282		41,186
Subtotal | Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	1,979,184		1,761,002
Operating segment | Commercial and Residential Lending Segment
Assets:
Cash and cash equivalents	7,078		68,593
Restricted cash	29,474		18,556
Loans held-for-investment, net	14,950,568		16,038,930
Loans held-for-sale	2,499,681		2,763,458
Investment securities	1,237,362		1,250,893
Properties, net	469,343		463,492
Investments in unconsolidated entities	25,207		25,326
Goodwill	0		0
Intangible assets	14,153		11,908
Derivative assets	123,662		101,082
Accrued interest receivable	160,815		151,852
Other assets	394,099		170,177
VIE assets, at fair value	0		0
Total Assets	19,911,442		21,064,267
Liabilities:
Dividends payable	0		0
Derivative liabilities	15,901		21,523
Secured financing agreements, net	9,974,212		10,804,970
Collateralized loan obligations and single asset securitization, net	2,702,506		2,862,211
Unsecured senior notes, net	0		0
VIE liabilities, at fair value	0		0
Total Liabilities	12,958,650		13,835,601
Temporary Equity: Redeemable non-controlling interests	0		0
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	0		0
Additional paid-in capital	1,522,081		2,124,496
Treasury stock	0		0
Retained earnings (accumulated deficit)	5,416,479		5,083,100
Accumulated other comprehensive income	14,114		20,955
Total Starwood Property Trust, Inc. Stockholders’ Equity	6,952,674		7,228,551
Non-controlling interests in consolidated subsidiaries	118		115
Total Permanent Equity	6,952,792		7,228,666
Total Liabilities and Equity	19,911,442		21,064,267
Operating segment | Commercial and Residential Lending Segment | Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	266,031		146,897
Operating segment | Commercial and Residential Lending Segment | Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	0		0
Operating segment | Commercial and Residential Lending Segment | Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	0		0
Operating segment | Infrastructure Lending Segment
Assets:
Cash and cash equivalents	35,247		31,153
Restricted cash	22,178		31,133
Loans held-for-investment, net	2,274,318		2,352,932
Loans held-for-sale	0		0
Investment securities	19,582		66,204
Properties, net	0		0
Investments in unconsolidated entities	48,224		47,078
Goodwill	119,409		119,409
Intangible assets	0		0
Derivative assets	134		122
Accrued interest receivable	9,574		9,856
Other assets	6,306		3,614
VIE assets, at fair value	0		0
Total Assets	2,534,972		2,661,501
Liabilities:
Dividends payable	0		0
Derivative liabilities	0		105
Secured financing agreements, net	935,043		1,042,679
Collateralized loan obligations and single asset securitization, net	815,768		814,013
Unsecured senior notes, net	0		0
VIE liabilities, at fair value	0		0
Total Liabilities	1,772,696		1,877,453
Temporary Equity: Redeemable non-controlling interests	0		0
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	0		0
Additional paid-in capital	616,063		683,258
Treasury stock	0		0
Retained earnings (accumulated deficit)	146,213		100,790
Accumulated other comprehensive income	0		0
Total Starwood Property Trust, Inc. Stockholders’ Equity	762,276		784,048
Non-controlling interests in consolidated subsidiaries	0		0
Total Permanent Equity	762,276		784,048
Total Liabilities and Equity	2,534,972		2,661,501
Operating segment | Infrastructure Lending Segment | Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	21,885		20,656
Operating segment | Infrastructure Lending Segment | Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	0		0
Operating segment | Infrastructure Lending Segment | Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	0		0
Operating segment | Property Segment
Assets:
Cash and cash equivalents	37,281		31,194
Restricted cash	997		981
Loans held-for-investment, net	0		0
Loans held-for-sale	0		0
Investment securities	0		0
Properties, net	851,713		864,778
Investments in unconsolidated entities	0		0
Goodwill	0		0
Intangible assets	26,375		29,613
Derivative assets	2,640		1,803
Accrued interest receivable	1,298		863
Other assets	51,914		54,313
VIE assets, at fair value	0		0
Total Assets	2,951,402		2,744,547
Liabilities:
Dividends payable	0		0
Derivative liabilities	0		0
Secured financing agreements, net	791,461		789,719
Collateralized loan obligations and single asset securitization, net	0		0
Unsecured senior notes, net	0		0
VIE liabilities, at fair value	0		0
Total Liabilities	804,185		801,435
Temporary Equity: Redeemable non-controlling interests	409,659		362,790
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	0		0
Additional paid-in capital	(428,536)		(405,955)
Treasury stock	0		0
Retained earnings (accumulated deficit)	1,957,453		1,777,643
Accumulated other comprehensive income	0		0
Total Starwood Property Trust, Inc. Stockholders’ Equity	1,528,917		1,371,688
Non-controlling interests in consolidated subsidiaries	208,641		208,634
Total Permanent Equity	1,737,558		1,580,322
Total Liabilities and Equity	2,951,402		2,744,547
Operating segment | Property Segment | Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	12,724		11,716
Operating segment | Property Segment | Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	0		0
Operating segment | Property Segment | Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	1,979,184		1,761,002
Operating segment | Investing and Servicing Segment
Assets:
Cash and cash equivalents	9,840		39,023
Restricted cash	4,746		5,259
Loans held-for-investment, net	9,319		9,577
Loans held-for-sale	102,584		21,136
Investment securities	1,106,436		1,165,628
Properties, net	84,735		121,716
Investments in unconsolidated entities	33,050		33,030
Goodwill	140,437		140,437
Intangible assets	61,435		66,310
Derivative assets	6,580		5,614
Accrued interest receivable	1,770		1,105
Other assets	19,533		12,929
VIE assets, at fair value	0		0
Total Assets	1,580,465		1,621,764
Liabilities:
Dividends payable	0		0
Derivative liabilities	0		0
Secured financing agreements, net	539,820		543,256
Collateralized loan obligations and single asset securitization, net	0		0
Unsecured senior notes, net	0		0
VIE liabilities, at fair value	0		0
Total Liabilities	575,818		589,633
Temporary Equity: Redeemable non-controlling interests	0		0
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	0		0
Additional paid-in capital	(680,659)		(646,662)
Treasury stock	0		0
Retained earnings (accumulated deficit)	1,531,338		1,514,119
Accumulated other comprehensive income	0		0
Total Starwood Property Trust, Inc. Stockholders’ Equity	850,679		867,457
Non-controlling interests in consolidated subsidiaries	153,968		164,674
Total Permanent Equity	1,004,647		1,032,131
Total Liabilities and Equity	1,580,465		1,621,764
Operating segment | Investing and Servicing Segment | Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	35,998		46,377
Operating segment | Investing and Servicing Segment | Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	0		0
Operating segment | Investing and Servicing Segment | Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	0		0
Corporate
Assets:
Cash and cash equivalents	105,873		91,098
Restricted cash	178,556		65,143
Loans held-for-investment, net	0		0
Loans held-for-sale	0		0
Investment securities	0		0
Properties, net	0		0
Investments in unconsolidated entities	0		0
Goodwill	0		0
Intangible assets	0		0
Derivative assets	0		0
Accrued interest receivable	88		5,120
Other assets	54,590		56,444
VIE assets, at fair value	0		0
Total Assets	339,107		217,805
Liabilities:
Dividends payable	152,737		151,511
Derivative liabilities	69,756		69,776
Secured financing agreements, net	1,338,203		1,342,074
Collateralized loan obligations and single asset securitization, net	0		0
Unsecured senior notes, net	2,456,583		2,329,211
VIE liabilities, at fair value	0		0
Total Liabilities	4,112,638		4,007,111
Temporary Equity: Redeemable non-controlling interests	0		0
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	3,205		3,181
Additional paid-in capital	4,827,013		4,051,950
Treasury stock	(138,022)		(138,022)
Retained earnings (accumulated deficit)	(8,465,727)		(7,706,415)
Accumulated other comprehensive income	0		0
Total Starwood Property Trust, Inc. Stockholders’ Equity	(3,773,531)		(3,789,306)
Non-controlling interests in consolidated subsidiaries	0		0
Total Permanent Equity	(3,773,531)		(3,789,306)
Total Liabilities and Equity	339,107		217,805
Corporate | Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	71,077		73,353
Corporate | Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	24,282		41,186
Corporate | Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	0		0
Securitization VIEs
Assets:
Cash and cash equivalents	0		0
Restricted cash	0		0
Loans held-for-investment, net	0		0
Loans held-for-sale	0		0
Investment securities	(1,641,787)		(1,666,921)
Properties, net	0		0
Investments in unconsolidated entities	(14,557)		(13,542)
Goodwill	0		0
Intangible assets	(35,974)		(39,058)
Derivative assets	0		0
Accrued interest receivable	(285)		(275)
Other assets	0		0
VIE assets, at fair value	44,668,904		52,453,041
Total Assets	42,976,301		50,733,245
Liabilities:
Dividends payable	0		0
Derivative liabilities	0		0
Secured financing agreements, net	(20,858)		(21,166)
Collateralized loan obligations and single asset securitization, net	0		0
Unsecured senior notes, net	0		0
VIE liabilities, at fair value	42,997,104		50,754,355
Total Liabilities	42,976,246		50,733,189
Temporary Equity: Redeemable non-controlling interests	0		0
Starwood Property Trust, Inc. Stockholders’ Equity:
Common stock	0		0
Additional paid-in capital	0		0
Treasury stock	0		0
Retained earnings (accumulated deficit)	0		0
Accumulated other comprehensive income	0		0
Total Starwood Property Trust, Inc. Stockholders’ Equity	0		0
Non-controlling interests in consolidated subsidiaries	55		56
Total Permanent Equity	55		56
Total Liabilities and Equity	42,976,301		50,733,245
Securitization VIEs | Nonrelated Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	0		0
Securitization VIEs | Related Party
Liabilities:
Accounts payable, accrued expenses and other liabilities	0		0
Securitization VIEs | Primary Beneficiary
Assets:
Investments of consolidated affordable housing fund	$ 0		$ 0