PREMISES AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 207,578		$ 207,578		$ 232,693
Total premises and equipment, net	59,980		59,980		45,631
Depreciation and amortization expense	7,900	$ 8,300	17,315	$ 17,049
Computer hardware and software
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	169,684		169,684		182,215
Office equipment and other
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	4,006		4,006		7,384
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	9,710		9,710		13,313
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	24,178		24,178		29,781
Excluding Right-to-use Assets
Property, Plant and Equipment [Line Items]
Less: Accumulated depreciation and amortization	(175,861)		(175,861)		(187,062)
Total premises and equipment, net	31,717		31,717		45,631
Right-to-use Assets
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	34,503		34,503		0
Less: Accumulated depreciation and amortization	(6,240)		(6,240)		0
Total premises and equipment, net	$ 28,263		$ 28,263		$ 0