Capital Stock (Details)	9 Months Ended		40 Months Ended
	Sep. 30, 2020 USD ($) director common_share	Sep. 30, 2019 USD ($) $ / shares	Feb. 29, 2020 USD ($)	Feb. 28, 2020 USD ($)	Nov. 30, 2016 USD ($)
Class of Stock [Line Items]
Classes of common shares | common_share	2
Stock repurchased during period, value		$ 584,000
Minimum
Class of Stock [Line Items]
Minimum number of directors up for election to entitle shareholders to vote | director	0.3333
Maximum
Class of Stock [Line Items]
Minimum number of directors up for election to entitle shareholders to vote | director	3
Common stock, Class A
Class of Stock [Line Items]
Stock repurchase program, authorized amount				$ 100,000,000	$ 100,000,000
Stock repurchased during period, value	$ 0	$ 600,000	$ 50,300,000
Common stock, Class A | Minimum
Class of Stock [Line Items]
Stock repurchased during period (in dollars per share) | $ / shares		$ 15.54
Common stock, Class A | Maximum
Class of Stock [Line Items]
Stock repurchased during period (in dollars per share) | $ / shares		$ 18.72