Quarterly report pursuant to Section 13 or 15(d)

ACCOUNTING POLICIES (Details)

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ACCOUNTING POLICIES (Details) - USD ($)
$ in Thousands
 3 Months Ended
Jan. 01, 2018
Mar. 31, 2018
Mar. 31, 2017
Jun. 30, 2018
Dec. 31, 2017
Business Acquisition [Line Items]          
Cash paid in acquisition   $ 6,170 $ 0    
Goodwill   724,106     $ 298,528
Affordable Housing Projects [Abstract]          
Affordable housing projects, recognized amortization   235 223    
Affordable housing projects, tax credits   283 $ 309    
Affordable housing projects, investment amount   11,600     11,000
Affordable housing projects, liability   $ 8,300     $ 7,300
Xenith          
Business Acquisition [Line Items]          
Fair value of total consideration transferred $ 800,979        
Number of shares equivalent to each share of acquired entity 0.9354        
Number of common shares issued 21,922,077        
Cash paid in acquisition $ 6,170        
Goodwill 425,577        
Acquired amortizable intangible assets $ 38,470        
Acquired amortizable assets, useful life 10 years        
Customer Relationships | Xenith          
Business Acquisition [Line Items]          
Acquired amortizable intangible assets $ 38,500        
Accounting Standards Update 2017-12 | Forecast          
Business Acquisition [Line Items]          
Held-to-maturity securities, transferred security, at carrying value       $ 200,000