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v3.19.3.a.u2

Pension, Savings, and Other Employee Benefits - Pension Plan and Savings Plan (Details) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Nov. 30, 2017 pension_plan
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Contributions to qualified plans |  | $ 509 | $ 353 | $ 5,100 |
Pension Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined benefit plan, benefit obligation |  | 835,874 | 765,309 | 840,884 |
Fair value of plan assets |  | 826,070 | 730,953 | 811,244 |
Employer contributions |  | 3,510 | 3,948 |  |
Qualified pension |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Contributions to qualified plans |  | $ 0 |  |  |
Qualified pension | Pension Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Estimated social security benefits age |  | 65 years |  |  |
Qualified pension | Capital Bank Financial Corporation | Pension Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Number of additional qualified pension plans | pension_plan |  |  |  |  | 2
Defined benefit plan, benefit obligation |  |  | 17,100 |  |
Fair value of plan assets |  |  | 16,500 |  |
Employer contributions | $ 500 |  |  |  |
Nonqualified pension | Pension Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Employer contributions |  | $ 5,200 |  |  |
Expected pension contribution |  | 5,200 |  |  |
Flexible Benefits Contribution |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Employer contributions |  | $ 27,700 | $ 29,300 | $ 23,000 |
Savings Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Employer investment in qualified defined contribution plan |  | 100.00% |  |  |
Maximum percent of employee pre-tax contributions that may be matched by the Company (percent) |  | 6.00% |  |  |

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