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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									97,226,027	81,902,524	61,998,089
Basic (in dollars per share)	$ 0.24	$ 0.69	$ 0.40	$ 0.53	$ 0.41	$ 0.28	$ 0.28	$ 0.18	$ 1.85	$ 1.16	$ 1.08
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									97,226,027	81,902,524	61,998,089
Diluted weighted average number of shares of Class A common stock outstanding (in shares)									97,652,065	109,704,880	107,638,788
Diluted (in dollars per share)	$ 0.24	$ 0.67	$ 0.40	$ 0.53	$ 0.40	$ 0.28	$ 0.26	$ 0.18	$ 1.84	$ 1.13	$ 1.06
Class A Common Stock
Numerator:
Net income (loss) attributable to Class A common shareholders	$ 24,103	$ 66,630	$ 38,407	$ 50,875	$ 36,106	$ 23,587	$ 22,113	$ 13,470	$ 180,015	$ 95,276	$ 66,727
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									97,226,027	81,902,524	61,998,089
Basic (in dollars per share)									$ 1.85	$ 1.16	$ 1.08
Numerator:
Net income (loss) attributable to Class A common shareholders	$ 24,103	$ 66,630	$ 38,407	$ 50,875	$ 36,106	$ 23,587	$ 22,113	$ 13,470	$ 180,015	$ 95,276	$ 66,727
Amounts attributable to operating partnership’s share of Ladder Capital Corp net income (loss)									0	30,378	47,130
Additional corporate tax (expense) benefit									0	(1,608)	299
Diluted Net income (loss) available for Class A common shareholders									$ 180,015	$ 124,046	$ 114,156
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									97,226,027	81,902,524	61,998,089
Shares issuable relating to converted Class B common shareholders (in shares)									0	27,773,765	45,118,668
Incremental shares of unvested Class A restricted stock (in shares)									426,038	28,591	522,031
Diluted weighted average number of shares of Class A common stock outstanding (in shares)									97,652,065	109,704,880	107,638,788
Diluted (in dollars per share)									$ 1.84	$ 1.13	$ 1.06