Share-Based Incentives Class B rollforward (Details) - shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding, beginning of year	100,000,000
Shares outstanding, end of year	100,000,000	100,000,000
Class B Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding, beginning of year	345,644	255,492
Granted	117,929	90,152
Purchased	18,875
Repurchased	(200,680)
Shares outstanding, end of year	281,768	345,644
Restricted Class B shares \| Class B Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding, beginning of year	161,810	71,658
Granted	117,929	90,152
Purchased	0
Repurchased	(100,407)
Shares outstanding, end of year	179,332	161,810
Unrestricted Class B shares \| Class B Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding, beginning of year	183,834	183,834
Granted	0	0
Purchased	18,875
Repurchased	(100,273)
Shares outstanding, end of year	102,436	183,834

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- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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+ References

No definition available.

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- Definition

Number of shares issued under share-based payment arrangement.

+ 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
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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