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Regulatory Matters - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
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Sep. 30, 2017 | Dec. 31, 2005 | Jun. 30, 2003 | Dec. 31, 2018 | Dec. 31, 2017
Regulatory Capital Requirements [Abstract] |  |  |  |  |
Proceeds from (repurchase of) trust preferred securities | $ (8) | $ 18 | $ 18 | $ 10 | $ 10
Tier 1 common equity, adequately capitalized ratio, conservation buffer |  |  |  | 2.50% |

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- Definition Tier One Common Equity Capital Required for Capital Adequacy to Risk Based Assets, Conservation Buffer + References No definition available. + Details
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- Definition The cash inflow from issuance of trust preferred securities, net of the cash outflow for repurchasing trust preferred securities, by a business trust or other special purpose entity, mainly established by a bank holding entity, to third party investors. The trust's assets are deeply subordinated debentures of the bank holding entity. Most trust preferred securities are subject to a mandatory redemption upon the repayment of the debentures. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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