PREMISES AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
PREMISES AND EQUIPMENT, NET
Premises and equipment, gross		$ 236,464	$ 232,870
Less: Accumulated depreciation and amortization		(163,191)	(129,397)
Total		73,273	103,473
Depreciation and amortization expense		36,447	36,788	$ 36,470
Impairment of premises and equipment	$ 4,100	0	0
Computer hardware and software
PREMISES AND EQUIPMENT, NET
Premises and equipment, gross		179,567	164,877
Office equipment and other
PREMISES AND EQUIPMENT, NET
Premises and equipment, gross		9,388	20,188
Furniture and fixtures
PREMISES AND EQUIPMENT, NET
Premises and equipment, gross		14,092	13,997
Leasehold improvements
PREMISES AND EQUIPMENT, NET
Premises and equipment, gross		$ 33,417	$ 33,808