Consolidated Statements of Cash Flows - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Statement of Cash Flows [Abstract]    
NET CASH PROVIDED BY OPERATING ACTIVITIES $ 32,371 $ 47,508
INVESTING ACTIVITIES    
Net decrease (increase) in loans held for investment 19,923 (63,701)
Debt securities available-for-sale:    
Proceeds from maturities, prepayments and calls 53,496 59,043
Purchases of securities (540,624) (41,742)
Debt securities held-to-maturity:    
Proceeds from maturities, prepayments and calls 17,121 24,367
Purchases of securities (15,343) (16,023)
Equity securities:    
Purchases of securities (558)  
Proceeds from bank-owned life insurance 3,506  
Purchases of premises and equipment-net (328) (2,311)
Net cash used in investing activities (462,807) (40,367)
FINANCING ACTIVITIES    
Increase in deposits 183,012 105,344
Proceeds from Federal Home Loan Bank borrowings 375,000 170,000
Repayment of Federal Home Loan Bank borrowings (156,261) (201,825)
Increase (decrease) in other short-term borrowings 27,848 (25,733)
Decrease in federal funds purchased (5,000) (58,000)
Dividends paid to common shareholders (11,450) (10,539)
Issuance of common stock 560 526
Net cash provided by (used in) financing activities 413,709 (20,227)
Net decrease in cash and cash equivalents (16,727) (13,086)
Cash and cash equivalents at beginning of the period 117,572 128,170
Cash and cash equivalents at end of the period 100,845 115,084
SUPPLEMENTAL DISCLOSURES    
Interest paid on deposits and other borrowings $ 12,496 9,441
Income taxes paid   250
Transfers of loans to other real estate owned   $ 77