INVESTMENTS IN CONSUMER LOANS - Others' Interest in Equity of Consumer Loan Companies (Details) - USD ($) $ 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
Noncontrolling Interest [Line Items]
Total Consumer Loan Companies equity	$ 4,690,205				$ 3,260,100				$ 4,690,205	$ 3,260,100
Noncontrolling interests in equity of consolidated subsidiaries	105,957				208,077				105,957	208,077
Noncontrolling Interests in Income of Consolidated Subsidiaries	12,068	$ 13,600	$ 15,671	$ 15,780	16,908	$ 32,178	$ 24,975	$ 4,202	57,119	78,263	$ 13,246
Consumer Loan Companies
Noncontrolling Interest [Line Items]
Total Consumer Loan Companies equity	$ 74,071				$ 75,311				74,071	75,311
Net Consumer Loan Companies income (loss)									$ 98,692	$ 81,992
Consumer Loan Companies
Noncontrolling Interest [Line Items]
Others’ ownership interest	46.50%				46.50%				46.50%	46.50%
Noncontrolling interests in equity of consolidated subsidiaries	$ 34,466				$ 35,020				$ 34,466	$ 35,020
Noncontrolling Interests in Income of Consolidated Subsidiaries									$ 45,892	$ 38,127