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Employee Incentive Plans (Narrative) (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended | 146 Months Ended
--- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018 | Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 10.00% |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match | 50.00% |  |  |
Defined Contribution Plan Vesting Period | 6 years |  |  |
401(k) plan contribution expense | $ 2 | $ 2 |  |
Maximum shares of stock distributable under 2007 Stock Incentive Plan | 30,000,000 |  |  | 30,000,000
Shares granted to external directors |  |  |  | 25,636
Stock Incentive Plan Granted Shares Adjustment |  |  | 640 |
2007 Stock Incentive Plan Compensation Expense | $ 30 | $ 29 |  |
Estimated Future 2007 Stock Incentive Plan Compensation Expense | $ 31 |  |  | $ 31
Post employment shares distribution |  |  |  | 976,879
2007 Stock Incentive Plan (Shares) |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting Percentage, description | •10% on the first vesting date, which is on or about May 9 of each year; and•an additional 15% on each of the following six anniversaries of the first vesting, assuming continued employment with the Company and compliance with non-competition and other applicable covenants. |  |  |
2007 Stock Incentive Plan (Shares) | External Director [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period | 5 years |  |  |
2007 Stock Incentive Plan (Shares) | Commencing One Year After Grant Date [Member] | External Director [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage per year | 20.00% |  |  |

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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