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Shareholders' Equity - AOCI Components (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2016 | Sep. 30, 2016
Repurchase of shares |  |
Repurchase of common stock (in shares) | 0 | 0
After-tax amounts: |  |
Stockholders' Equity Attributable to Parent | $ 4,475,915 | $ 4,560,925
Maximum |  |
Repurchase of shares |  |
Number of common shares authorized to be repurchased | 4,000,000 |
Unrealized appreciation (depreciation) on securities |  |
Pre-tax amounts: |  |
Accumulated other comprehensive income (loss) before tax | $ 53,293 | 33,051
After-tax amounts: |  |
Stockholders' Equity Attributable to Parent | 33,311 | 20,899
Defined benefit pension plan |  |
Pre-tax amounts: |  |
Accumulated other comprehensive income (loss) before tax | (33,537) | (34,112)
After-tax amounts: |  |
Stockholders' Equity Attributable to Parent | (20,737) | (21,103)
Accumulated Other Comprehensive Income (loss) |  |
Pre-tax amounts: |  |
Accumulated other comprehensive income (loss) before tax | 19,756 | (1,061)
After-tax amounts: |  |
Stockholders' Equity Attributable to Parent | $ 12,574 | $ (204)

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- Definition Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(30)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 4.E) -URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(31)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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