SEGMENT REPORTING - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment			4
Segment Reporting Information [Line Items]
Noninterest expense	$ 124,262	$ 81,743	$ 313,437	$ 245,542
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Noninterest expense	77,177	44,566	181,499	131,708
Operating Segments | Mortgage Banking
Segment Reporting Information [Line Items]
Noninterest expense	47,085	35,442	127,130	108,203
Adjustment | Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Noninterest expense	(4,200)	(1,600)	(11,600)	(5,200)
Adjustment | Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Noninterest expense	(3,900)	(3,700)	(11,100)	(9,900)
Adjustment | Operating Segments | Mortgage Banking
Segment Reporting Information [Line Items]
Noninterest expense	8,100	4,900	22,000	14,000
Adjustment | Operating Segments | Financial Advisory
Segment Reporting Information [Line Items]
Noninterest expense	$ 0	$ 444	$ 760	$ 1,100