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Fair Value Option and Fair Value Measurements - Changes in Level 3 (Details) (USD $) In Thousands, unless otherwise specified | 9 Months Ended |  |  |  |  | 9 Months Ended
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Sep. 30, 2014 Interest rate swap agreements net of swap credit valuation | Sep. 30, 2013 Interest rate swap agreements net of swap credit valuation | Sep. 30, 2013 Collateralized debt obligations | Sep. 30, 2014 Asset-backed securities | Sep. 30, 2013 Asset-backed securities | Sep. 30, 2014 States and political subdivisions | Dec. 31, 2013 States and political subdivisions | Sep. 30, 2013 States and political subdivisions | Dec. 31, 2012 States and political subdivisions | Sep. 30, 2014 Mortgage servicing rights | Sep. 30, 2013 Mortgage servicing rights
Changes in Level 3 |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  | $ 9,957 | $ 154,137 |  | $ 125 | $ 125 | $ 132 | $ 132 | $ 5,807 | $ 4,116
Total gains or losses |  |  |  |  |  |  |  |  |  |  |
Included in earnings (or changes in net assets) |  |  | 178 | 3,178 | 485 |  |  |  |  | (761) | 81
Included in other comprehensive income |  |  | 1,898 | (1,748) | (1,487) |  |  |  |  |  |
Purchases, issuances, sales, and settlements |  |  |  |  |  |  |  |  |  |  |
Purchases |  |  |  | 63,704 | 168,753 |  |  |  |  |  |
Issuances |  |  |  |  |  |  |  |  |  | 594 | 1,259
Settlements |  |  | (946) |  |  |  |  |  |  |  |
Sales |  |  |  | (135,490) | (20,539) |  |  |  |  |  |
Ending balance |  |  | 11,087 | 83,781 | 147,212 | 125 | 125 | 132 | 132 | 5,640 | 5,456
Changes in Level 3 (liabilities) |  |  |  |  |  |  |  |  |  |  |
Beginning balance | (6) | (47) |  |  |  |  |  |  |  |  |
Included in earnings (or changes in net assets) | 6 | 34 |  |  |  |  |  |  |  |  |
Ending balance |  | $ (13) |  |  |  |  |  |  |  |  |

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