VARIABLE INTEREST ENTITIES - Summary of Unconsolidated VIEs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Funded commitments	$ 57,300
Aggregate funding commitment	100,000
Loss on investments in alternative energy partnerships, net	31,510	$ 0	$ 0
Investment tax credit	33,400
Unfunded commitments	42,700
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Loss on investments in alternative energy partnerships, net	31,500
Total unconsolidated assets	152,072
Investment tax credit	33,400
Equipment, net of depreciation	151,721
Other assets	351
Maximum loss exposure	68,298
Total unconsolidated liabilities	0
Variable Interest Entity, Not Primary Beneficiary | Other Assets
Variable Interest Entity [Line Items]
Total unconsolidated assets	$ 25,600