QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands													3 Months Ended								12 Months Ended
	Nov. 07, 2017	Sep. 01, 2017	Jun. 01, 2017	Mar. 01, 2017	Dec. 02, 2016	Sep. 01, 2016	Jun. 01, 2016	Apr. 01, 2016	Dec. 01, 2015	Sep. 01, 2015	Jun. 08, 2015	Mar. 12, 2015	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
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Interest income													$ 73,352	$ 66,833	$ 65,970	$ 57,512	$ 60,721	$ 60,284	$ 55,766	$ 59,601	$ 263,667	$ 236,372	$ 241,539
Net interest income after provision for loan losses													31,795	29,348	30,309	26,097	28,517	29,599	27,214	29,915	117,549	115,245	127,636
Other income (loss)													69,436	39,141	47,475	30,418	89,212	69,335	11,835	(7,070)
Costs and expenses													52,804	39,244	40,120	38,260	45,335	40,615	37,405	35,162	170,428	158,517	168,166
Income (loss) before taxes													48,427	29,245	37,664	18,255	72,394	58,319	1,644	(12,317)	133,591	120,040	160,691
Income tax expense (benefit)													3,057	(576)	6,606	(1,375)	773	8,721	(2,301)	(873)	7,712	6,320	14,557
Net income (loss)													45,370	29,821	31,058	19,630					125,879	113,720	146,134
Net (income) loss attributable to noncontrolling interest in consolidated joint ventures													(92)	265	(77)	(322)	(298)	439	(235)	232	(226)	138	(1,568)
Net (income) loss attributable to predecessor unitholders																	0	0	0	0
Net (income) loss attributable to noncontrolling interest in operating partnership													$ (9,172)	$ (6,499)	$ (8,868)	$ (5,838)	$ (29,467)	$ (22,429)	$ (908)	$ 5,673	$ (30,377)	$ (47,131)	$ (70,745)
Earnings Per Share, Basic and Diluted [Abstract]
Basic (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
Diluted (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
Dividends per share of common stock (in dollars per share)													$ 0.315	$ 0.3	$ 0.3	$ 0.3	$ 0.46	$ 0.275	$ 0.275	$ 0.275
Additional return on equity from Company's investments																					$ 0	$ 1,017	$ 294
Income (Loss), Including Portion Attributable to Noncontrolling Interest, before Tax																	$ 71,621	$ 49,598	$ 3,945	$ (11,444)
Noncontrolling Interests in Consolidated Joint Ventures
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)																					226	(138)	1,568
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Interest income														$ 72,763	$ 66,136
Net interest income after provision for loan losses														30,156	30,532
Other income (loss)														39,141	21,571
Costs and expenses														39,244	40,120
Income (loss) before taxes														30,053	11,983
Income tax expense (benefit)														(400)	(1,449)
Net (income) loss attributable to noncontrolling interest in consolidated joint ventures														265	(77)
Net (income) loss attributable to noncontrolling interest in operating partnership														$ (6,679)	$ (2,693)
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)														$ 0.28	$ 0.13
Diluted (in dollars per share)														0.28	0.13
Dividends per share of common stock (in dollars per share)														$ 0.3	$ 0.3
Income (Loss), Including Portion Attributable to Noncontrolling Interest, before Tax														$ 30,453	$ 13,432
Class A common stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss) 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
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)																					$ 1.16	$ 1.08	$ 1.43
Diluted (in dollars per share)																					1.13	1.06	1.42
Dividends per share of common stock (in dollars per share)	$ 0.315	$ 0.3	$ 0.3	$ 0.3	$ 0.46	$ 0.275	$ 0.275	$ 0.275	$ 1.45	$ 0.275	$ 0.25	$ 0.25									$ 1.215	$ 1.285	$ 2.225
Class A common stock | Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss) attributable to Class A common shareholders														$ 24,039	$ 10,662