Segment Data - Balance sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Assets:
Cash and cash equivalents	$ 811,656	$ 478,388
Restricted cash	119,737	95,643
Loans held-for-investment, net of credit loss allowances of $97,187 and $33,415 ($274,758 and $671,572 held at fair value)	10,488,936	10,586,074
Loans held-for-sale	1,174,934	884,150
Investment securities	777,972	810,238
Properties, net	2,253,070	2,266,440
Intangible assets	82,005	85,700
Investment in unconsolidated entities	87,334	84,329
Goodwill	259,846	259,846
Derivative assets	101,448	28,943
Accrued interest receivable	58,537	64,087
Other assets	203,909	211,323
Total Assets	77,577,189	78,042,336
Liabilities:
Accounts payable, accrued expenses and other liabilities	221,669	212,006
Related-party payable	39,266	40,925
Dividends payable	137,529	137,427
Derivative liabilities	5,118	8,740
Secured financing agreements, net	9,689,683	8,906,048
Collateralized loan obligations, net	928,683	928,060
Unsecured senior notes, net	1,930,584	1,928,622
Total Liabilities	72,759,838	72,905,322
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,894	2,874
Additional paid-in capital	5,159,069	5,132,532
Treasury stock	(133,024)	(104,194)
Accumulated other comprehensive income (loss)	35,884	50,932	$ 55,798	$ 58,660
Retained earnings (accumulated deficit)	(616,765)	(381,719)
Total Starwood Property Trust, Inc. Stockholders' Equity	4,448,058	4,700,425
Non-controlling interests in consolidated subsidiaries	369,293	436,589
Total Equity	4,817,351	5,137,014	$ 4,916,967	$ 4,900,189
Total Liabilities and Equity	77,577,189	78,042,336
Infrastructure Lending Segment
Assets:
Goodwill	119,400	119,400
Investing and Servicing Segment
Assets:
Goodwill	140,400	140,400
Operating Segments and Corporate
Assets:
Cash and cash equivalents	807,222	477,167
Restricted cash	119,737	95,643
Loans held-for-investment, net of credit loss allowances of $97,187 and $33,415 ($274,758 and $671,572 held at fair value)	10,488,936	10,586,074
Loans held-for-sale	1,174,934	884,150
Investment securities	2,095,745	2,215,275
Properties, net	2,253,070	2,266,440
Intangible assets	108,963	111,947
Investment in unconsolidated entities	107,200	104,966
Goodwill	259,846	259,846
Derivative assets	101,448	28,943
Accrued interest receivable	59,295	64,893
Other assets	203,924	211,330
Total Assets	17,780,320	17,306,674
Liabilities:
Accounts payable, accrued expenses and other liabilities	221,594	211,922
Related-party payable	39,266	40,925
Dividends payable	137,529	137,427
Derivative liabilities	5,118	8,740
Secured financing agreements, net	9,703,633	8,919,998
Collateralized loan obligations, net	928,683	928,060
Unsecured senior notes, net	1,930,584	1,928,622
Total Liabilities	12,966,407	12,175,694
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,894	2,874
Additional paid-in capital	5,159,069	5,132,532
Treasury stock	(133,024)	(104,194)
Accumulated other comprehensive income (loss)	35,884	50,932
Retained earnings (accumulated deficit)	(616,765)	(381,719)
Total Starwood Property Trust, Inc. Stockholders' Equity	4,448,058	4,700,425
Non-controlling interests in consolidated subsidiaries	365,855	430,555
Total Equity	4,813,913	5,130,980
Total Liabilities and Equity	17,780,320	17,306,674
Operating segment | Commercial and Residential Lending Segment
Assets:
Cash and cash equivalents	22,910	26,278
Restricted cash	50,331	36,135
Loans held-for-investment, net of credit loss allowances of $97,187 and $33,415 ($274,758 and $671,572 held at fair value)	9,106,441	9,187,332
Loans held-for-sale	886,076	605,384
Investment securities	955,614	992,974
Properties, net	26,585	26,834
Investment in unconsolidated entities	50,017	46,921
Derivative assets	57,238	14,718
Accrued interest receivable	49,942	45,996
Other assets	61,109	59,170
Total Assets	11,266,263	11,041,742
Liabilities:
Accounts payable, accrued expenses and other liabilities	33,645	30,594
Derivative liabilities	3,740	7,698
Secured financing agreements, net	5,611,239	5,038,876
Collateralized loan obligations, net	928,683	928,060
Total Liabilities	6,577,307	6,005,228
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	1,159,771	1,522,360
Accumulated other comprehensive income (loss)	35,948	50,996
Retained earnings (accumulated deficit)	3,493,119	3,463,158
Total Starwood Property Trust, Inc. Stockholders' Equity	4,688,838	5,036,514
Non-controlling interests in consolidated subsidiaries	118
Total Equity	4,688,956	5,036,514
Total Liabilities and Equity	11,266,263	11,041,742
Operating segment | Infrastructure Lending Segment
Assets:
Cash and cash equivalents	40	2,209
Restricted cash	43,679	41,967
Loans held-for-investment, net of credit loss allowances of $97,187 and $33,415 ($274,758 and $671,572 held at fair value)	1,381,271	1,397,448
Loans held-for-sale	101,895	119,528
Investment securities	44,141	45,153
Investment in unconsolidated entities	25,862	25,862
Goodwill	119,409	119,409
Derivative assets	6	7
Accrued interest receivable	4,949	3,134
Other assets	5,108	6,101
Total Assets	1,726,360	1,760,818
Liabilities:
Accounts payable, accrued expenses and other liabilities	11,933	6,443
Derivative liabilities	1,292	750
Secured financing agreements, net	1,190,995	1,217,066
Total Liabilities	1,204,220	1,224,259
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	531,986	529,668
Retained earnings (accumulated deficit)	(9,846)	6,891
Total Starwood Property Trust, Inc. Stockholders' Equity	522,140	536,559
Total Equity	522,140	536,559
Total Liabilities and Equity	1,726,360	1,760,818
Operating segment | Property Segment
Assets:
Cash and cash equivalents	28,137	30,123
Restricted cash	7,362	7,171
Properties, net	2,014,007	2,029,024
Intangible assets	45,331	47,303
Derivative assets	98	3
Accrued interest receivable		133
Other assets	76,776	82,910
Total Assets	2,171,711	2,196,667
Liabilities:
Accounts payable, accrued expenses and other liabilities	48,748	48,370
Secured financing agreements, net	1,698,044	1,698,334
Total Liabilities	1,746,792	1,746,704
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	229,223	208,650
Retained earnings (accumulated deficit)	(31,451)	5,431
Total Starwood Property Trust, Inc. Stockholders' Equity	197,772	214,081
Non-controlling interests in consolidated subsidiaries	227,147	235,882
Total Equity	424,919	449,963
Total Liabilities and Equity	2,171,711	2,196,667
Operating segment | Investing and Servicing Segment
Assets:
Cash and cash equivalents	36,913	61,693
Restricted cash	18,365	10,370
Loans held-for-investment, net of credit loss allowances of $97,187 and $33,415 ($274,758 and $671,572 held at fair value)	1,224	1,294
Loans held-for-sale	186,963	159,238
Investment securities	1,095,990	1,177,148
Properties, net	212,478	210,582
Intangible assets	63,632	64,644
Investment in unconsolidated entities	31,321	32,183
Goodwill	140,437	140,437
Derivative assets	2,250	7
Accrued interest receivable	1,047	2,388
Other assets	52,119	54,238
Total Assets	1,842,739	1,914,222
Liabilities:
Accounts payable, accrued expenses and other liabilities	48,090	73,021
Related-party payable	5	5
Derivative liabilities	86	292
Secured financing agreements, net	692,941	574,507
Total Liabilities	741,122	647,825
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	(200,489)	(123,210)
Accumulated other comprehensive income (loss)	(64)	(64)
Retained earnings (accumulated deficit)	1,163,580	1,194,998
Total Starwood Property Trust, Inc. Stockholders' Equity	963,027	1,071,724
Non-controlling interests in consolidated subsidiaries	138,590	194,673
Total Equity	1,101,617	1,266,397
Total Liabilities and Equity	1,842,739	1,914,222
Corporate
Assets:
Cash and cash equivalents	719,222	356,864
Derivative assets	41,856	14,208
Accrued interest receivable	3,357	13,242
Other assets	8,812	8,911
Total Assets	773,247	393,225
Liabilities:
Accounts payable, accrued expenses and other liabilities	79,178	53,494
Related-party payable	39,261	40,920
Dividends payable	137,529	137,427
Secured financing agreements, net	510,414	391,215
Unsecured senior notes, net	1,930,584	1,928,622
Total Liabilities	2,696,966	2,551,678
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,894	2,874
Additional paid-in capital	3,438,578	2,995,064
Treasury stock	(133,024)	(104,194)
Retained earnings (accumulated deficit)	(5,232,167)	(5,052,197)
Total Starwood Property Trust, Inc. Stockholders' Equity	(1,923,719)	(2,158,453)
Total Equity	(1,923,719)	(2,158,453)
Total Liabilities and Equity	773,247	393,225
LNR VIEs
Assets:
Cash and cash equivalents	4,434	1,221
Investment securities	(1,317,773)	(1,405,037)
Intangible assets	(26,958)	(26,247)
Investment in unconsolidated entities	(19,866)	(20,637)
Accrued interest receivable	(758)	(806)
Other assets	(15)	(7)
Total Assets	59,796,869	60,735,662
Liabilities:
Accounts payable, accrued expenses and other liabilities	75	84
Secured financing agreements, net	(13,950)	(13,950)
Total Liabilities	59,793,431	60,729,628
Starwood Property Trust, Inc. Stockholders' Equity:
Non-controlling interests in consolidated subsidiaries	3,438	6,034
Total Equity	3,438	6,034
Total Liabilities and Equity	59,796,869	60,735,662
Primary beneficiary
Assets:
Total Assets	61,157,805	62,187,175
Liabilities:
Total Liabilities	59,807,306	60,743,494
Primary beneficiary | LNR VIEs
Assets:
Total Assets	61,157,805	62,187,175
Liabilities:
Total Liabilities	$ 59,807,306	$ 60,743,494