Capital Stock (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Sep. 12, 2020	Mar. 31, 2021	Mar. 31, 2019	Mar. 31, 2018	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	3,000,000.0
Stock repurchased and retired (in shares)			127,180	1,093,259
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%
Class A Common Stock
Class of Stock [Line Items]
Shares outstanding (in shares)		41,583,430			40,335,113
Stock Repurchase Program, Number of Shares Authorized to be Repurchased						2,500,000
Stock repurchased and retired (in shares)		72,700
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		1,900,000
Class B Common Stock
Class of Stock [Line Items]
Shares outstanding (in shares)		20,646,913			21,760,686
Director [Member]
Class of Stock [Line Items]
Common shares issued (in shares)		604