VARIABLE INTEREST ENTITIES - Summary of Unconsolidated VIEs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Variable Interest Entity [Line Items]
Funded commitments	$ 30,927	$ 0
Loss on investments in alternative energy partnerships	8,682	$ 0
Total amount funded	88,300
Aggregate funding commitment	200,000
Tax credit	8,800
Alternative investments unfunded investment commitments	111,700
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Loss on investments in alternative energy partnerships	8,700
Tax credit	8,800
Cash	224		$ 0
Equipment, net of depreciation	203,226		151,721
Other assets	8,337		351
Total unconsolidated assets	211,787		152,072
Total unconsolidated liabilities	651		0
Maximum loss exposure	159,365		$ 68,298
Variable Interest Entity, Not Primary Beneficiary | Other Assets
Variable Interest Entity [Line Items]
Total unconsolidated assets	$ 47,600