Capital Stock (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended			9 Months Ended
	Sep. 12, 2020	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jun. 11, 2019
Class of Stock [Line Items]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	5,500,000
Incremental Common Shares Attributable to Dilutive Effect of Accelerated Share Repurchase Agreements	3,000,000
Stock repurchased and retired (in shares)		574		1,445,300	128,038	2,539,041
Accelerated Share Repurchases, Adjustment to Recorded Amount					$ 2.9
Shares repurchased, average cost per share (in dollars per share)					$ 39.69
Shares repurchased during the period as percentage of shares authorized for repurchase (percent)					1.30%
Common shares issued (in shares)					19,081	19,491
Class A Common Stock
Class of Stock [Line Items]
Shares outstanding (in shares)		41,715,627			41,715,627		40,335,113
Stock Repurchase Program, Number of Shares Authorized to be Repurchased								2,500,000
Stock repurchased and retired (in shares)			0		72,700
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		1,900,000			1,900,000
Class B Common Stock
Class of Stock [Line Items]
Shares outstanding (in shares)		20,515,516			20,515,516		21,760,686
Director [Member]
Class of Stock [Line Items]
Common shares issued (in shares)					19,081
Director [Member] | Class A Common Stock
Class of Stock [Line Items]
Dividend, Share-based Payment Arrangement, Paid-in-Kind					$ 0.9