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Retirement Plans (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Retirement Benefits [Abstract] |  |  |  |
Employer contribution match, percent match |  |  | 100.00% |
Employer contribution match, percentage of employee contribution |  |  | 6.00% |
Defined contributions plan expense | $ 3 | $ 3 | $ 10 | $ 10
Cost or expenses included in compensation and benefit expense | 4 | $ 5 | $ 15 | $ 13
Employer contributions, amount | $ 22 |  |  |
Funded status, percentage | 100.00% |  |  |

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- Definition Defined Contribution Plan, Funded Percentage + References No definition available. + Details
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Balance Type: | na
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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
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- Definition Amount of cost (reversal of cost) for pension and other postretirement benefits. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration