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Changes in Fair Value of MSRs (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Mortgage servicing rights |  |  |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |  |  |
Mortgage Banking Income | [1] | $ (70) | $ (30,988) | $ (224) | $ (68,081)
[1] | Included in "Non-interest income."

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