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Fair Value Measurements (Details 4) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Dec. 31, 2017
Valuation Methodology |  |
Investment securities, available-for-sale | $ 942,076 | $ 904,033
Level 3 |  |
Valuation Methodology |  |
Investment securities, available-for-sale | 2,863 | 2,865
Recurring | Level 3 |  |
Valuation Methodology |  |
Investment securities, available-for-sale | 2,863 | 2,865
Recurring | Level 3 | Discounted cash flows | Direct placement municipal securities |  |
Valuation Methodology |  |
Investment securities, available-for-sale | $ 2,155 | $ 2,155
Recurring | Level 3 | Discounted cash flows | Direct placement municipal securities | Minimum |  |
Unobservable Inputs |  |
Credit spread assumption (as a percent) | 2.26% | 2.21%
Recurring | Level 3 | Discounted cash flows | Direct placement municipal securities | Maximum |  |
Unobservable Inputs |  |
Credit spread assumption (as a percent) | 3.08% | 2.93%
Recurring | Level 3 | Discounted cash flows | Foreign government |  |
Valuation Methodology |  |
Investment securities, available-for-sale | $ 708 | $ 710
Recurring | Level 3 | Discounted cash flows | Foreign government | Minimum |  |
Unobservable Inputs |  |
Market yield assumption (as a percent) | 0.22% | 0.35%
Recurring | Level 3 | Discounted cash flows | Foreign government | Maximum |  |
Unobservable Inputs |  |
Market yield assumption (as a percent) | 1.33% | 1.23%
Non-recurring | Level 3 | Commercial loans |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 20.00% |
Non-recurring | Level 3 | Minimum | Commercial loans |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 40.00% |
Non-recurring | Level 3 | Maximum | Commercial loans |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 75.00% |
Non-recurring | Level 3 | Trade publications | Aircraft |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 10.00% |
Non-recurring | Level 3 | Auction values | Autos |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 10.00% |
Non-recurring | Level 3 | Trade publications and auction values | Medium and heavy duty trucks |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 15.00% |
Non-recurring | Level 3 | Trade publications and auction values | Construction equipment |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 20.00% |
Non-recurring | Level 3 | Appraisals | Real estate |  |
Unobservable Inputs |  |
Discount rate (as a percent) | 20.00% |

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