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Deposits (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Deposits, by Type [Abstract] |  |  |  |
Non-interest bearing demand | $ 3,426,500,000 | $ 3,158,300,000 |  |
Interest bearing: |  |  |  |
Demand | 3,195,400,000 | 2,957,500,000 |  |
Savings | 3,591,600,000 | 3,247,900,000 |  |
Total | 651,100,000 | 547,600,000 |  |
Time, other | 798,900,000 | 769,400,000 |  |
Total interest bearing | 8,237,000,000.0 | 7,522,400,000 | $ 7,522,400,000 | $ 7,034,900,000
Total deposits | 11,663,500,000 | 10,680,700,000 |  |
Brokered time deposits | 2,900,000 | 24,100,000 | 0 |
Time deposits obtained through Certificate of Deposit Account Registry Service (CDARS) | 117,700,000 | 87,100,000 |  |
Time deposits of $250,000 or more | 278,400,000 | 221,000,000.0 |  |
FDIC deposit insurance limit | 250,000,000 |  |  |
Time, $100 and Over |  |  |  |
Due within 3 months or less | 101,600,000 |  |  |
Due after 3 months and within 6 months | 140,800,000 |  |  |
Due after 6 months and within 12 months | 273,700,000 |  |  |
Due within 2021 | 104,000,000.0 |  |  |
Total | 651,100,000 | 547,600,000 |  |
Total Time |  |  |  |
Due within 3 months or less | 323,600,000 |  |  |
Due after 3 months and within 6 months | 301,400,000 |  |  |
Due after 6 months and within 12 months | 515,900,000 |  |  |
Due within 2021 | 220,400,000 |  |  |
Total | 1,450,000,000.0 |  |  |
Interest expense, time deposits, $100,000 or more | 11,500,000 | $ 5,000,000.0 | $ 3,500,000 |
Contractual Maturities, Time Deposits, $100,000 or More, after 2 years | 23,600,000 |  |  |
Time Deposits Maturities, after Next Two Years | 64,000,000.0 |  |  |
Contractual Maturities, Time Deposits, $100,000 or More, after 3 years | 3,500,000 |  |  |
Time Deposits Maturities, after Next Three Years | 13,900,000 |  |  |
Contractual Maturities, Time Deposits, $100,000 or More, after 5 years and thereafter | 3,900,000 |  |  |
Time Deposits Maturities, after Next Five Years and Thereafter | $ 10,800,000 |  |  |

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