Stock Compensation - Options Rollforward (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Beginning balance, shares	3,332,705	4,926,668	5,156,976
Granted, shares	443,170	838,912	505,122
Exercised, shares	(641,706)	(1,548,484)	(2,781,055)
Forfeited, shares	(301,370)	(884,391)	(448,928)
Ending balance, shares	2,832,799	3,332,705	4,926,668
Shares exercisable, shares	1,755,821
Weighted Average Exercise Price Per Share
Beginning balance, weighted average share price, usd per share	$ 18.22	$ 14.56	$ 20.40
Granted, weighted average share price, usd per share	20.94	32.16	27.78
Exercised, weighted average exercise price, usd per share	10.56	13.79	11.67
Forfeited, weighted average exercise price, usd per share	26.07	18.8	15.01
Ending balance, weighted average share price, usd per share	19.55	$ 18.22	$ 14.56
Exercisable, weighted average exercise price, usd per share	$ 16.47
Options outstanding, intrinsic value	$ 17.0
Options exercisable, intrinsic value	$ 14.6
Weighted average remaining contract term, years	5 years 10 months 24 days
Exercisable, weighted average term, years	4 years 7 months 6 days
Class B-1 Common Stock
Shares
Granted, shares			2,494,553
Weighted Average Exercise Price Per Share
Granted, weighted average share price, usd per share			$ 11.13

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.