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Fair Value Measurements - Recurring and Nonrecurring (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | $ 1,441,935 |  | $ 1,922,894
Total financial assets | 3,165,027 |  | 3,364,450
Recurring |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 1,441,935 |  | 1,922,894
Interest rate contracts | 2,560 |  | 20,895
Total financial assets | 1,444,495 |  | 1,943,789
Total financial liabilities | 4,685 |  | 55,554
Recurring | Interest rate contracts |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 2,560 |  | 20,895
Recurring | Commercial loan hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 49 |  | 3,312
Recurring | Long term borrowing hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 2,076 |  | 31,347
Recurring | Equity securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 522 |  | 101,824
Recurring | U.S. government and agency securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 247,268 |  | 259,351
Recurring | Municipal bonds |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 26,459 |  | 27,670
Recurring | Obligations of foreign governments |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Corporate debt securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 208,025 |  | 461,138
Recurring | Agency pass-through certificates |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 906,847 |  | 993,041
Recurring | Commercial MBS |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 52,814 |  | 79,870
Recurring | Level 1 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 522 |  | 101,824
Interest rate contracts | 0 |  | 0
Total financial assets | 522 |  | 101,824
Total financial liabilities | 0 |  | 0
Recurring | Level 1 | Interest rate contracts |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 0 |  | 0
Recurring | Level 1 | Commercial loan hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 0 |  | 0
Recurring | Level 1 | Long term borrowing hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 0 |  | 0
Recurring | Level 1 | Equity securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 522 |  | 101,824
Recurring | Level 1 | U.S. government and agency securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 1 | Municipal bonds |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 1 | Obligations of foreign governments |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 1 | Corporate debt securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 1 | Agency pass-through certificates |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 1 | Commercial MBS |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 2 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 1,441,413 |  | 1,821,070
Interest rate contracts | 2,560 |  | 20,895
Total financial assets | 1,443,973 |  | 1,841,965
Total financial liabilities | 4,685 |  | 55,554
Recurring | Level 2 | Interest rate contracts |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 2,560 |  | 20,895
Recurring | Level 2 | Commercial loan hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 49 |  | 3,312
Recurring | Level 2 | Long term borrowing hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 2,076 |  | 31,347
Recurring | Level 2 | Equity securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 2 | U.S. government and agency securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 247,268 |  | 259,351
Recurring | Level 2 | Municipal bonds |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 26,459 |  | 27,670
Recurring | Level 2 | Obligations of foreign governments |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 2 | Corporate debt securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 208,025 |  | 461,138
Recurring | Level 2 | Agency pass-through certificates |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 906,847 |  | 993,041
Recurring | Level 2 | Commercial MBS |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 52,814 |  | 79,870
Recurring | Level 3 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Interest rate contracts | 0 |  | 0
Total financial assets | 0 |  | 0
Total financial liabilities | 0 |  | 0
Recurring | Level 3 | Interest rate contracts |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 0 |  | 0
Recurring | Level 3 | Commercial loan hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 0 |  | 0
Recurring | Level 3 | Long term borrowing hedge |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Interest rate contracts | 0 |  | 0
Recurring | Level 3 | Equity securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 3 | U.S. government and agency securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 3 | Municipal bonds |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 3 | Obligations of foreign governments |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 3 | Corporate debt securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 3 | Agency pass-through certificates |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | 0
Recurring | Level 3 | Commercial MBS |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Available-for-sale securities, at fair value | 0 |  | $ 0
Nonrecurring |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 5,652 | $ 15,669 |
Nonrecurring | Changes Measurement |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Loss related to impaired loans and real estate held for sale, measured on nonrecurring basis | (663) | (3,436) |
Nonrecurring | Impaired loans |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 3,353 | 8,524 |
Nonrecurring | Impaired loans | Changes Measurement |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Loss related to impaired loans and real estate held for sale, measured on nonrecurring basis | (422) | (1,681) |
Nonrecurring | Real Estate Owned |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 2,299 | 7,145 |
Nonrecurring | Real Estate Owned | Changes Measurement |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Loss related to impaired loans and real estate held for sale, measured on nonrecurring basis | (241) | (1,755) |
Nonrecurring | Level 1 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 0 | 0 |
Nonrecurring | Level 1 | Impaired loans |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 0 | 0 |
Nonrecurring | Level 1 | Real Estate Owned |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 0 | 0 |
Nonrecurring | Level 2 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 0 | 0 |
Nonrecurring | Level 2 | Impaired loans |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 0 | 0 |
Nonrecurring | Level 2 | Real Estate Owned |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 0 | 0 |
Nonrecurring | Level 3 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 5,652 | 15,669 |
Nonrecurring | Level 3 | Impaired loans |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | 3,353 | 8,524 |
Nonrecurring | Level 3 | Real Estate Owned |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Assets, nonrecurring | $ 2,299 | $ 7,145 |

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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13495-108611 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313 + Details
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