Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Earnings Per Share [Abstract]
Net income (loss)	$ (20,468)	$ 34,631	$ 28,400	$ (71,744)	$ (23,616)	$ (94,493)	$ 42,562	$ (189,853)
Net (income) loss attributable to noncontrolling interests:
Investment Entities	5			61			(2)	3,746
Operating Partnership	0			1,626			(1,013)	4,016
Net income (loss) attributable to BrightSpire Capital, Inc. common stockholders	(20,463)			(70,057)			41,547	(182,091)
Numerator:
Net (income) loss allocated to participating securities (non-vested shares)	0			0			(1,142)	0
Net income attributable to BrightSpire Capital, Inc. common stockholders	$ (20,463)			$ (70,057)			$ 40,405	$ (182,091)
Denominator:
Weighted average shares of common stock outstanding - basic (in shares)	126,564,000			128,693,000			127,551,000	128,430,000
Weighted average shares of common stock outstanding - diluted (in shares)	126,564,000			128,693,000			129,432,000	128,430,000
Net income (loss) per common share - basic (in dollars per share)	$ (0.16)			$ (0.54)			$ 0.32	$ (1.42)
Net income (loss) per common share - diluted (in dollars per share)	$ (0.16)			$ (0.54)			$ 0.31	$ (1.42)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding (in shares)	2,673,154						2,673,154		1,754,094
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding (in shares)	2,401,154			1,550,862			2,401,154	1,550,862	1,482,094
Antidilutive securities excluded from computation of earnings per share (in shares)	2,401,154			1,550,862				1,550,862