Segment Data - Balance sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Assets:
Cash and cash equivalents	$ 222,518	$ 615,522
Restricted cash	40,016	35,233
Loans held-for-investment, net	6,230,819	5,847,995
Loans held-for-sale	340,266	63,279
Loans transferred as secured borrowings	35,000	35,000
Investment securities	730,171	807,618
Properties, net	1,937,968	1,944,720
Intangible assets	202,094	219,248
Investment in unconsolidated entities	201,823	204,605
Goodwill	140,437	140,437
Derivative assets	71,040	89,361
Accrued interest receivable	32,759	28,224
Other assets	107,979	101,763
VIE assets, at fair value	60,185,851	67,123,261
Total Assets	70,478,741	77,256,266
Liabilities:
Accounts payable, accrued expenses and other liabilities	151,405	198,134
Related-party payable	25,997	37,818
Dividends payable	126,048	125,075
Derivative liabilities	1,567	3,904
Secured financing agreements, net	4,414,917	4,154,126
Unsecured senior notes, net	2,033,384	2,011,544
Secured borrowings on transferred loans	35,000	35,000
VIE liabilities, at fair value	59,147,068	66,130,592
Total Liabilities	65,935,386	72,696,193
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,648	2,639
Additional paid-in capital	4,689,698	4,691,180
Treasury stock	(92,104)	(92,104)
Accumulated other comprehensive income (loss)	40,067	36,138	$ 33,457	$ 29,729
Retained earnings (accumulated deficit)	(138,700)	(115,579)
Total Starwood Property Trust, Inc. Stockholders' Equity	4,501,609	4,522,274
Non-controlling interests in consolidated subsidiaries	41,746	37,799
Total Equity	4,543,355	4,560,073	$ 4,090,863	$ 4,170,943
Total Liabilities and Equity	70,478,741	77,256,266
Investment and Servicing Segment
Assets:
Goodwill		0
Operating Segments and Corporate
Assets:
Cash and cash equivalents	221,282	614,374
Restricted cash	40,016	35,233
Loans held-for-investment, net	6,230,819	5,847,995
Loans held-for-sale	340,266	63,279
Loans transferred as secured borrowings	35,000	35,000
Investment securities	1,729,845	1,766,642
Properties, net	1,937,968	1,944,720
Intangible assets	235,127	253,486
Investment in unconsolidated entities	210,406	212,227
Goodwill	140,437	140,437
Derivative assets	71,040	89,361
Accrued interest receivable	32,759	28,224
Other assets	110,688	104,408
Total Assets	11,335,653	11,135,386
Liabilities:
Accounts payable, accrued expenses and other liabilities	150,482	197,248
Related-party payable	25,997	37,818
Dividends payable	126,048	125,075
Derivative liabilities	1,567	3,904
Secured financing agreements, net	4,438,617	4,177,826
Unsecured senior notes, net	2,033,384	2,011,544
Secured borrowings on transferred loans	35,000	35,000
Total Liabilities	6,811,095	6,588,415
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,648	2,639
Additional paid-in capital	4,689,698	4,691,180
Treasury stock	(92,104)	(92,104)
Accumulated other comprehensive income (loss)	40,067	36,138
Retained earnings (accumulated deficit)	(138,700)	(115,579)
Total Starwood Property Trust, Inc. Stockholders' Equity	4,501,609	4,522,274
Non-controlling interests in consolidated subsidiaries	22,949	24,697
Total Equity	4,524,558	4,546,971
Total Liabilities and Equity	11,335,653	11,135,386
Operating segment | Lending Segment
Assets:
Cash and cash equivalents	654	7,085
Restricted cash	19,784	17,885
Loans held-for-investment, net	6,210,717	5,827,553
Loans held-for-sale	189,334
Loans transferred as secured borrowings	35,000	35,000
Investment securities	714,699	776,072
Investment in unconsolidated entities	31,125	30,874
Derivative assets	26,594	45,282
Accrued interest receivable	31,950	25,831
Other assets	17,775	13,470
Total Assets	7,277,632	6,779,052
Liabilities:
Accounts payable, accrued expenses and other liabilities	23,132	20,769
Derivative liabilities	1,113	3,388
Secured financing agreements, net	2,485,056	2,258,462
Secured borrowings on transferred loans	35,000	35,000
Total Liabilities	2,544,301	2,317,619
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	2,391,134	2,218,671
Accumulated other comprehensive income (loss)	46,825	44,903
Retained earnings (accumulated deficit)	2,284,352	2,186,727
Total Starwood Property Trust, Inc. Stockholders' Equity	4,722,311	4,450,301
Non-controlling interests in consolidated subsidiaries	11,020	11,132
Total Equity	4,733,331	4,461,433
Total Liabilities and Equity	7,277,632	6,779,052
Operating segment | Investment and Servicing Segment
Assets:
Cash and cash equivalents	46,711	38,798
Restricted cash	10,349	8,202
Loans held-for-investment, net	20,102	20,442
Loans held-for-sale	150,932	63,279
Investment securities	1,015,146	990,570
Properties, net	277,253	277,612
Intangible assets	111,728	125,327
Investment in unconsolidated entities	53,974	56,376
Goodwill	140,437	140,437
Derivative assets	1,713	1,186
Accrued interest receivable	809	2,393
Other assets	51,043	59,503
Total Assets	1,880,197	1,784,125
Liabilities:
Accounts payable, accrued expenses and other liabilities	43,985	68,603
Related-party payable	94	440
Derivative liabilities	454	516
Secured financing agreements, net	450,181	426,683
Total Liabilities	494,714	496,242
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	917,208	883,761
Accumulated other comprehensive income (loss)	(396)	(437)
Retained earnings (accumulated deficit)	456,742	390,994
Total Starwood Property Trust, Inc. Stockholders' Equity	1,373,554	1,274,318
Non-controlling interests in consolidated subsidiaries	11,929	13,565
Total Equity	1,385,483	1,287,883
Total Liabilities and Equity	1,880,197	1,784,125
Operating segment | Property Segment
Assets:
Cash and cash equivalents	15,048	7,701
Restricted cash	9,883	9,146
Properties, net	1,660,715	1,667,108
Intangible assets	123,399	128,159
Investment in unconsolidated entities	125,307	124,977
Derivative assets	42,733	42,893
Other assets	40,373	29,569
Total Assets	2,017,458	2,009,553
Liabilities:
Accounts payable, accrued expenses and other liabilities	57,615	81,873
Secured financing agreements, net	1,207,281	1,196,830
Total Liabilities	1,264,896	1,278,703
Starwood Property Trust, Inc. Stockholders' Equity:
Additional paid-in capital	713,255	696,049
Accumulated other comprehensive income (loss)	(6,362)	(8,328)
Retained earnings (accumulated deficit)	45,669	43,129
Total Starwood Property Trust, Inc. Stockholders' Equity	752,562	730,850
Total Equity	752,562	730,850
Total Liabilities and Equity	2,017,458	2,009,553
Corporate
Assets:
Cash and cash equivalents	158,869	560,790
Other assets	1,497	1,866
Total Assets	160,366	562,656
Liabilities:
Accounts payable, accrued expenses and other liabilities	25,750	26,003
Related-party payable	25,903	37,378
Dividends payable	126,048	125,075
Secured financing agreements, net	296,099	295,851
Unsecured senior notes, net	2,033,384	2,011,544
Total Liabilities	2,507,184	2,495,851
Starwood Property Trust, Inc. Stockholders' Equity:
Common stock	2,648	2,639
Additional paid-in capital	668,101	892,699
Treasury stock	(92,104)	(92,104)
Retained earnings (accumulated deficit)	(2,925,463)	(2,736,429)
Total Starwood Property Trust, Inc. Stockholders' Equity	(2,346,818)	(1,933,195)
Total Equity	(2,346,818)	(1,933,195)
Total Liabilities and Equity	160,366	562,656
Investment and Servicing VIEs
Assets:
Cash and cash equivalents	1,236	1,148
Investment securities	(999,674)	(959,024)
Intangible assets	(33,033)	(34,238)
Investment in unconsolidated entities	(8,583)	(7,622)
Other assets	(2,709)	(2,645)
VIE assets, at fair value	60,185,851	67,123,261
Total Assets	59,143,088	66,120,880
Liabilities:
Accounts payable, accrued expenses and other liabilities	923	886
Secured financing agreements, net	(23,700)	(23,700)
VIE liabilities, at fair value	59,147,068	66,130,592
Total Liabilities	59,124,291	66,107,778
Starwood Property Trust, Inc. Stockholders' Equity:
Non-controlling interests in consolidated subsidiaries	18,797	13,102
Total Equity	18,797	13,102
Total Liabilities and Equity	$ 59,143,088	$ 66,120,880