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Acquisitions - Schedule of Recognized Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions |  | 3 Months Ended
--- | --- | ---
May 30, 2017 | Sep. 30, 2016
Cascade Bank Acquisition, As Recorded By Cascade Bank |  |
Business Acquisition [Line Items] |  |
Cash and cash equivalents | $ 246.8 |
Investment securities | 476.7 |
Loans held for investment | 2,111.0 |
Mortgage loans held for sale | 10.3 |
Allowance for loan losses | (24.0) |
Premises and equipment | 46.6 |
Other real estate owned (OREO) | 1.2 |
Core deposit intangible assets | 0.0 |
Deferred tax assets, net | 47.6 |
Other assets | 98.6 |
Total assets acquired | 3,014.8 |
Deposits | 2,669.9 |
Accounts payable and accrued expense | 62.2 |
Total liabilities assumed | 2,732.1 |
Net assets acquired | 282.7 |
Cascade Bank Acquisition, Fair Value Adjustments |  |
Business Acquisition [Line Items] |  |
Cash and cash equivalents | 0.0 |
Investment securities | 4.9 |
Loans held for investment | (31.7) |
Mortgage loans held for sale | 0.0 |
Allowance for loan losses | 24.0 |
Premises and equipment | 0.1 |
Other real estate owned (OREO) | 0.0 |
Core deposit intangible assets | 48.0 |
Deferred tax assets, net | (19.0) |
Other assets | 1.1 |
Total assets acquired | 27.4 |
Deposits | (0.9) |
Accounts payable and accrued expense | 1.9 |
Total liabilities assumed | 1.0 |
Net assets acquired | 26.4 |
Cascade Bank Acquisition, as Recorded by the Company |  |
Business Acquisition [Line Items] |  |
Cash and cash equivalents | 246.8 |
Investment securities | 481.6 |
Loans held for investment | 2,079.3 |
Mortgage loans held for sale | 10.3 |
Allowance for loan losses | 0.0 |
Premises and equipment | 46.7 |
Other real estate owned (OREO) | 1.2 |
Core deposit intangible assets | 48.0 |
Deferred tax assets, net | 28.6 |
Other assets | 99.7 |
Total assets acquired | 3,042.2 |
Deposits | 2,669.0 |
Accounts payable and accrued expense | 64.1 |
Total liabilities assumed | 2,733.1 |
Net assets acquired | 309.1 |
Cash | 155.0 |
Total consideration paid | 541.0 |
Reduction in goodwill |  | $ 0.3
Cascade Bank Acquisition, as Recorded by the Company | Class A Common Stock |  |
Business Acquisition [Line Items] |  |
Class A common stock | $ 386.0 |

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