EARNINGS PER SHARE - Schedule of Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									105,455,849	97,226,027	81,902,524
Basic net income (loss) per share of Class A common stock (in dollars per share)	$ 0.38	$ 0.26	$ 0.31	$ 0.21	$ 0.24	$ 0.69	$ 0.40	$ 0.53	$ 1.16	$ 1.85	$ 1.16
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									105,455,849	97,226,027	81,902,524
Diluted weighted average number of shares of Class A common stock outstanding (in shares)									106,399,783	97,652,065	109,704,880
Diluted net income (loss) per share of Class A common stock (in dollars per share)	$ 0.37	$ 0.26	$ 0.30	$ 0.21	$ 0.24	$ 0.67	$ 0.40	$ 0.53	$ 1.15	$ 1.84	$ 1.13
Class A Common Stock
Numerator:
Net income (loss) attributable to Class A common shareholders	$ 40,650	$ 27,577	$ 32,242	$ 22,175	$ 24,103	$ 66,630	$ 38,407	$ 50,875	$ 122,645	$ 180,015	$ 95,276
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									105,455,849	97,226,027	81,902,524
Basic net income (loss) per share of Class A common stock (in dollars per share)									$ 1.16	$ 1.85	$ 1.16
Numerator:
Net income (loss) attributable to Class A common shareholders	$ 40,650	$ 27,577	$ 32,242	$ 22,175	$ 24,103	$ 66,630	$ 38,407	$ 50,875	$ 122,645	$ 180,015	$ 95,276
Amounts attributable to operating partnership’s share of Ladder Capital Corp net income (loss)									0	0	30,378
Additional corporate tax (expense) benefit									0	0	(1,608)
Diluted net income (loss) attributable to Class A common shareholders									$ 122,645	$ 180,015	$ 124,046
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									105,455,849	97,226,027	81,902,524
Shares issuable relating to converted Class B common shareholders (in shares)									0	0	27,773,765
Diluted weighted average number of shares of Class A common stock outstanding (in shares)									106,399,783	97,652,065	109,704,880
Diluted net income (loss) per share of Class A common stock (in dollars per share)									$ 1.15	$ 1.84	$ 1.13
Restricted Stock | Class A Common Stock
Denominator:
Incremental shares of stock based compensation (in shares)									943,934	426,038	28,591
Stock Options | Class A Common Stock
Denominator:
Incremental shares of stock based compensation (in shares)									0	0	0