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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									81,902,524	61,998,089	51,702,188
Basic net income (loss) per share of Class A common stock (in dollars per share)	$ 0.41	$ 0.28	$ 0.28	$ 0.18	$ 0.64	$ 0.44	$ 0.05	$ (0.09)	$ 1.16	$ 1.08	$ 1.43
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									81,902,524	61,998,089	51,702,188
Diluted weighted average number of shares of Class A common stock outstanding (in shares)									109,704,880	107,638,788	51,870,808
Diluted net income per share of Class A common stock (in dollars per share)	$ 0.40	$ 0.28	$ 0.26	$ 0.18	$ 0.63	$ 0.44	$ 0.05	$ (0.09)	$ 1.13	$ 1.06	$ 1.42
Class A common stock
Numerator:
Net income attributable to Class A common shareholders	$ 36,106	$ 23,587	$ 22,113	$ 13,470	$ 41,856	$ 27,608	$ 2,802	$ (5,539)	$ 95,276	$ 66,727	$ 73,821
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									81,902,524	61,998,089	51,702,188
Basic net income (loss) per share of Class A common stock (in dollars per share)									$ 1.16	$ 1.08	$ 1.43
Numerator:
Net income attributable to Class A common shareholders	$ 36,106	$ 23,587	$ 22,113	$ 13,470	$ 41,856	$ 27,608	$ 2,802	$ (5,539)	$ 95,276	$ 66,727	$ 73,821
Amounts attributable to operating partnership’s share of Ladder Capital Corp net income (loss)									30,378	47,130	0
Additional corporate tax (expense) benefit									(1,608)	299	0
Diluted Net income (loss) available for Class A common shareholders									$ 124,046	$ 114,156	$ 73,821
Denominator:
Weighted average number of shares of Class A common stock outstanding (in shares)									81,902,524	61,998,089	51,702,188
Shares issuable relating to converted Class B common shareholders (in shares)									27,773,765	45,118,668	0
Incremental shares of unvested Class A restricted stock (in shares)									28,591	522,031	168,620
Diluted weighted average number of shares of Class A common stock outstanding (in shares)									109,704,880	107,638,788	51,870,808
Diluted net income per share of Class A common stock (in dollars per share)									$ 1.13	$ 1.06	$ 1.42