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Summary Of Significant Accounting Policies (Details) - USD ($) |  |  | 12 Months Ended
--- | --- | --- | ---
Oct. 31, 2017 | Jul. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |  |  |  |  |  |
Loan impairment threshold period |  |  |  | 90 days |  |
Threshold of reporting unit goodwill carrying value for further analysis |  |  |  | $ 0 |  |
Goodwill impairment charges | $ 0 | $ 0 |  |  |  |
Corporate tax rate |  |  |  | 35.00% |  |
Shares withheld from employee awards for tax withholding purposes |  |  |  | $ 214,744,000 | $ 61,601,000 | $ 65,021,000
Reclassification from Operating Activities to Financing Activities [Member] | ASU No. 2016-09 [Member] |  |  |  |  |  |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |  |  |  |  |  |
Shares withheld from employee awards for tax withholding purposes |  |  |  |  | $ 61,600,000 | $ 65,000,000
Scenario Forecast [Member] |  |  |  |  |  |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |  |  |  |  |  |
Corporate tax rate |  |  | 21.00% |  |  |
Office Equipment [Member] | Minimum [Member] |  |  |  |  |  |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |  |  |  |  |  |
Fixed assets, Useful life |  |  |  | 2 years |  |
Office Equipment [Member] | Maximum [Member] |  |  |  |  |  |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |  |  |  |  |  |
Fixed assets, Useful life |  |  |  | 7 years |  |
Building and Building Improvements [Member] | Minimum [Member] |  |  |  |  |  |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |  |  |  |  |  |
Fixed assets, Useful life |  |  |  | 3 years |  |
Building and Building Improvements [Member] | Maximum [Member] |  |  |  |  |  |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |  |  |  |  |  |
Fixed assets, Useful life |  |  |  | 39 years |  |

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