CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Treasury stock, shares issued (in shares)	5,498,228	4,568,002
Common Class A
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000,000.0	1,000,000,000
Common stock, shares issued (in shares)	167,604,348	160,833,463
Common stock, shares outstanding (in shares)	161,175,894	156,265,461	156,916,336	138,593,787
Treasury stock, shares issued (in shares)	5,498,228	4,568,002
Common Class B
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	21,285,533	21,285,533
Common stock, shares outstanding (in shares)	21,285,533	21,285,533