Common Stock (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) item shares	Dec. 31, 2018 USD ($) shares	Feb. 06, 2019 USD ($)	Jul. 27, 2015 USD ($)
Common Stock
Common Stock conversion ratio, at the option of the holder	1
Number of repurchase plans | item	2
Class A
Common Stock
Common Stock, votes per share (Number of votes)	1	1
Shares of Common Stock reserved for issuance under stock-based compensation plans | shares	2,343,195
Number of shares repurchased | shares	227,620	340,106
Cost of shares of Class A common stock repurchased	$ 19.5	$ 26.0
Class A | July 27, 2015
Common Stock
Value of shares of the entity's Class A common stock authorized to be repurchased				$ 100.0
Number of shares repurchased | shares	146,304	340,106
Cost of shares of Class A common stock repurchased	$ 11.8	$ 26.0
Class A | February 06, 2019
Common Stock
Value of shares of the entity's Class A common stock authorized to be repurchased			$ 150.0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 142.3
Number of shares repurchased | shares	81,316
Cost of shares of Class A common stock repurchased	$ 7.7
Class B
Common Stock
Common Stock, votes per share (Number of votes)	10	10
Shares of Common Stock reserved for conversion | shares	6,279,290