Segment Data - Balance sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Assets:
Cash and cash equivalents	$ 335,219	$ 368,815	$ 360,720	$ 255,187
Restricted cash	48,375	23,069
Loans held-for-investment, net	6,187,654	5,973,079
Loans held-for-sale	154,225	203,865
Loans transferred as secured borrowings	88,512	86,573
Investment securities	649,364	724,947
Properties, net	1,154,975	919,225
Intangible assets	180,476	201,570
Investment in unconsolidated entities	196,637	199,201
Goodwill	140,437	140,437
Derivative assets	36,938	45,091
Accrued interest receivable	35,972	34,314
Other assets	111,860	102,479
VIE assets, at fair value	85,115,662	76,675,689
Total Assets	94,436,306	85,698,354
Liabilities:
Accounts payable, accrued expenses and other liabilities	139,286	156,805
Related-party payable	24,157	40,955
Dividends payable	114,839	114,947
Derivative liabilities	16,202	5,196
Secured financing agreements, net	4,480,960	3,980,699
Convertible senior notes, net	1,329,072	1,323,795
Secured borrowings on transferred loans	89,905	88,000
VIE liabilities, at fair value	84,151,022	75,817,014
Total Liabilities	90,345,443	81,527,411
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,422	2,410
Additional paid-in capital	4,210,904	4,192,844
Treasury stock	(92,104)	(72,381)
Accumulated other comprehensive income (loss)	33,457	29,729	39,362	55,896
Retained earnings (accumulated deficit)	(100,201)	(12,286)
Total Starwood Property Trust, Inc. Stockholders' Equity	4,054,478	4,140,316
Non-controlling interests in consolidated subsidiaries	36,385	30,627
Total Equity	4,090,863	4,170,943	$ 3,880,116	$ 3,882,912
Total Liabilities and Equity	94,436,306	85,698,354
Operating Segments and Corporate
Assets:
Cash and cash equivalents	334,174	367,837
Restricted cash	48,375	23,069
Loans held-for-investment, net	6,187,654	5,973,079
Loans held-for-sale	154,225	203,865
Loans transferred as secured borrowings	88,512	86,573
Investment securities	1,565,258	1,550,166
Properties, net	1,154,975	919,225
Intangible assets	207,841	213,399
Investment in unconsolidated entities	204,071	206,426
Goodwill	140,437	140,437
Derivative assets	36,938	45,091
Accrued interest receivable	35,920	34,314
Other assets	114,071	104,536
Total Assets	10,272,451	9,868,017
Liabilities:
Accounts payable, accrued expenses and other liabilities	138,566	156,116
Related-party payable	24,157	40,955
Dividends payable	114,839	114,947
Derivative liabilities	16,202	5,196
Secured financing agreements, net	4,480,960	3,980,699
Convertible senior notes, net	1,329,072	1,323,795
Secured borrowings on transferred loans	89,905	88,000
Total Liabilities	6,193,701	5,709,708
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,422	2,410
Additional paid-in capital	4,210,904	4,192,844
Treasury stock	(92,104)	(72,381)
Accumulated other comprehensive income (loss)	33,457	29,729
Retained earnings (accumulated deficit)	(100,201)	(12,286)
Total Starwood Property Trust, Inc. Stockholders' Equity	4,054,478	4,140,316
Non-controlling interests in consolidated subsidiaries	24,272	17,993
Total Equity	4,078,750	4,158,309
Total Liabilities and Equity	10,272,451	9,868,017
Operating segment | Lending Segment
Assets:
Cash and cash equivalents	103,942	83,836
Restricted cash	31,474	9,775
Loans held-for-investment, net	6,169,937	5,973,079
Loans transferred as secured borrowings	88,512	86,573
Investment securities	552,640	511,966
Investment in unconsolidated entities	30,311	30,827
Derivative assets	33,237	33,412
Accrued interest receivable	35,451	34,028
Other assets	14,640	7,938
Total Assets	7,060,144	6,771,434
Liabilities:
Accounts payable, accrued expenses and other liabilities	28,501	18,822
Derivative liabilities	12,551	5,190
Secured financing agreements, net	2,723,567	2,341,897
Secured borrowings on transferred loans	89,905	88,000
Total Liabilities	2,854,524	2,453,909
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	2,276,386	2,477,987
Accumulated other comprehensive income (loss)	33,569	37,242
Retained earnings (accumulated deficit)	1,884,190	1,790,705
Total Starwood Property Trust, Inc. Stockholders' Equity	4,194,145	4,305,934
Non-controlling interests in consolidated subsidiaries	11,475	11,591
Total Equity	4,205,620	4,317,525
Total Liabilities and Equity	7,060,144	6,771,434
Operating segment | Investment and Servicing Segment
Assets:
Cash and cash equivalents	70,684	62,649
Restricted cash	11,710	8,826
Loans held-for-investment, net	17,717
Loans held-for-sale	154,225	203,865
Investment securities	1,012,618	1,038,200
Properties, net	172,289	150,497
Intangible assets	147,495	152,278
Investment in unconsolidated entities	52,463	53,145
Goodwill	140,437	140,437
Derivative assets	2,911	2,087
Accrued interest receivable	469	286
Other assets	70,562	71,505
Total Assets	1,853,580	1,883,775
Liabilities:
Accounts payable, accrued expenses and other liabilities	51,774	90,399
Related-party payable	689	423
Derivative liabilities	2,106	6
Secured financing agreements, net	397,884	422,260
Total Liabilities	452,453	513,088
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	1,173,852	1,146,926
Accumulated other comprehensive income (loss)	(4,395)	(3,714)
Retained earnings (accumulated deficit)	218,873	221,073
Total Starwood Property Trust, Inc. Stockholders' Equity	1,388,330	1,364,285
Non-controlling interests in consolidated subsidiaries	12,797	6,402
Total Equity	1,401,127	1,370,687
Total Liabilities and Equity	1,853,580	1,883,775
Operating segment | Property Segment
Assets:
Cash and cash equivalents	15,486	2,944
Restricted cash	5,191	4,468
Properties, net	982,686	768,728
Intangible assets	60,346	61,121
Investment in unconsolidated entities	121,297	122,454
Derivative assets	790	9,592
Other assets	27,132	23,657
Total Assets	1,212,928	992,964
Liabilities:
Accounts payable, accrued expenses and other liabilities	42,329	25,427
Derivative liabilities	1,545
Secured financing agreements, net	712,782	568,738
Total Liabilities	756,656	594,165
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	456,658	394,465
Accumulated other comprehensive income (loss)	4,283	(3,799)
Retained earnings (accumulated deficit)	(4,669)	8,133
Total Starwood Property Trust, Inc. Stockholders' Equity	456,272	398,799
Total Equity	456,272	398,799
Total Liabilities and Equity	1,212,928	992,964
Corporate
Assets:
Cash and cash equivalents	144,062	218,408
Other assets	1,737	1,436
Total Assets	145,799	219,844
Liabilities:
Accounts payable, accrued expenses and other liabilities	15,962	21,468
Related-party payable	23,468	40,532
Dividends payable	114,839	114,947
Secured financing agreements, net	646,727	647,804
Convertible senior notes, net	1,329,072	1,323,795
Total Liabilities	2,130,068	2,148,546
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,422	2,410
Additional paid-in capital	304,008	173,466
Treasury stock	(92,104)	(72,381)
Retained earnings (accumulated deficit)	(2,198,595)	(2,032,197)
Total Starwood Property Trust, Inc. Stockholders' Equity	(1,984,269)	(1,928,702)
Total Equity	(1,984,269)	(1,928,702)
Total Liabilities and Equity	145,799	219,844
Investment and Servicing VIEs
Assets:
Cash and cash equivalents	1,045	978
Investment securities	(915,894)	(825,219)
Intangible assets	(27,365)	(11,829)
Investment in unconsolidated entities	(7,434)	(7,225)
Accrued interest receivable	52
Other assets	(2,211)	(2,057)
VIE assets, at fair value	85,115,662	76,675,689
Total Assets	84,163,855	75,830,337
Liabilities:
Accounts payable, accrued expenses and other liabilities	720	689
VIE liabilities, at fair value	84,151,022	75,817,014
Total Liabilities	84,151,742	75,817,703
Starwood Property Trust, Inc. Stockholders' Equity:
Non-controlling interests in consolidated subsidiaries	12,113	12,634
Total Equity	12,113	12,634
Total Liabilities and Equity	$ 84,163,855	$ 75,830,337