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INVESTMENTS (Narrative) (Detail) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2019 USD ($) security | Jun. 30, 2018 USD ($) | Jun. 30, 2019 USD ($) security | Jun. 30, 2018 USD ($) | Dec. 31, 2018 USD ($) security
Schedule of Investments [Line Items] |  |  |  |  |
Net unrealized gains (losses) on available-for-sale securities, net of tax | $ 3,912,000 |  | $ 3,912,000 |  | $ (17,826,000)
Deferred tax assets, unrealized losses on available for sale securities | $ 1,100,000 |  | 1,100,000 |  | $ 4,900,000
Payments to acquire investments |  |  | $ 98,800,000 | $ 100,600,000 |
AFS securities in unrealized loss positions, number of positions | security | 125 |  | 125 |  | 302
AFS and HTM securities in Continuous Unrealized Loss Position | $ 387,400,000 |  | $ 387,400,000 |  | $ 722,200,000
AFS and HTM Securities Unrealized Loss Accumulated in Investments | 5,200,000 |  | 5,200,000 |  | 24,600,000
Fair Value - 12 Months of More | $ 387,390,000 |  | $ 387,390,000 |  | $ 621,294,000
Unrealized Loss as a Percent of Fair Value | 1.40% |  | 1.40% |  | 3.40%
Carrying Value of Investments Sold | $ 45,800,000 | $ 9,900,000 | $ 45,800,000 | 9,900,000 |
Debt Securities, Available-for-sale, Gain (Loss) |  |  | 27,000 | 31,000 |
Security pledged as collateral, amortized cost | 667,300,000 |  | 667,300,000 |  | $ 734,100,000
Security pledged as collateral, fair value | 670,500,000 |  | 670,500,000 |  | 714,400,000
Unrealized loss, change in fair value of bank stock equity securities | (159,000) | 11,000 | 84,000 | $ (24,000) |
Gain on sale of other investment |  | $ 195,000 |  |  |
Mortgage Backed Securities and Collateralized Mortgage Obligations |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |
AFS and HTM Securities Unrealized Loss Accumulated in Investments | 5,200,000 |  | 5,200,000 |  | 23,300,000
Fair Value - 12 Months of More | 383,300,000 |  | 383,300,000 |  | 591,900,000
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |
Fair Value - 12 Months of More | 246,463,000 |  | 246,463,000 |  | 364,430,000
Collateralized Mortgage Obligations |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |
Fair Value - 12 Months of More | $ 136,876,000 |  | $ 136,876,000 |  | $ 227,461,000

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