Aggregate number of common shares reserved for future issuance.

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Description of voting rights of common stock. Includes eligibility to vote and votes per share owned. Include also, if any, unusual voting rights.

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Number, after forfeiture, of shares or units issued under share-based payment arrangement. Excludes shares or units issued under employee stock ownership plan (ESOP).

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The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Number Of Votes

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The increase in number of shares allowed to be repurchased per year. This amount is an addition to the balance of allowable share repurchases from the prior year and has been authorized by an entity's Board of Directors under a stock repurchase plan.

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Common Shareholders' Equity (Details)		1 Months Ended	12 Months Ended
Common Shareholders' Equity (Details)	Jan. 01, 2017 shares	Nov. 30, 2009 shares	Dec. 31, 2019 vote shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares
Series A Common Shares
Share repurchases
Number of votes \| vote			10
Voting rights for number of board of directors			75%
Common Shares
Share repurchases
Number of votes \| vote			1
Voting rights for number of board of directors			25%
Common Shares \| 401(k)
Share repurchases
Shares reserved (in shares)			67,000
Common Shares \| Treasury shares
Share repurchases
Repurchase authorization, cumulative shares authorized (in shares)			5,311,000
Common shareholders' equity, other disclosures
Shares reissued (in shares)			432,000	1,181,000	325,000
Common Shares \| Treasury shares \| Minimum
Share repurchases
Repurchase authorization, additional number of shares per year (in shares)	0
Common Shares \| Treasury shares \| Maximum
Share repurchases
Repurchase authorization, additional number of shares per year (in shares)	1,300,000	1,300,000