Common Shareholders' Equity (Details) $ / shares in Units, $ in Millions		1 Months Ended	12 Months Ended
	Jan. 01, 2017 shares	Nov. 30, 2009 shares	Dec. 31, 2024 USD ($) vote $ / shares shares	Dec. 31, 2022 USD ($)
Share repurchases
Purchase price | $			$ 55	$ 43
Treasury shares
Share repurchases
Purchase price | $			$ 55	$ 43
Series A Common Shares
Common shareholders' equity, other disclosures
Number of votes | vote			10
Voting rights for number of board of directors			75%
Common Shares
Share repurchases
Stock Repurchase Program Additional Number Of Shares Authorized To Be Repurchased Per Year		1,300,000
Repurchase of Common Shares			939,999
Purchase price | $			$ 55
Average cost per share | $ / shares			$ 58.06
Repurchase authorization, cumulative shares authorized (in shares)			986,942
Common shareholders' equity, other disclosures
Number of votes | vote			1
Voting rights for number of board of directors			25%
Common Shares | Maximum
Share repurchases
Stock Repurchase Program Additional Number Of Shares Authorized To Be Repurchased Per Year	1,300,000
Common Shares | Minimum
Share repurchases
Stock Repurchase Program Additional Number Of Shares Authorized To Be Repurchased Per Year	0
Common Shares | 401(k)
Common shareholders' equity, other disclosures
Shares reserved (in shares)			962,000