Equity - Schedule of Changes in Number of Shares of Common Stock Issued and Repurchased (Detail) - shares shares in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Common Stock | Class A
Balance at beginning of period (in shares)	18,508	18,100	15,664	15,281	18,100	15,281
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares	2	2	1	1
Share conversion - Class B to A	207	406	809	382
Balance at end of period (in shares)	18,717	18,508	16,474	15,664	18,717	16,474
Common Stock | Class B
Balance at beginning of period (in shares)	54,538	53,937	55,014	55,284	53,937	55,284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share conversion - Class B to A	(207)	(406)	(809)	(382)
Vesting of restricted share grants	173	719	4	40
Exercise of options		288	150	72
Balance at end of period (in shares)	54,504	54,538	54,359	55,014	54,504	54,359
Treasury Stock | Class A
Balance at beginning of period (in shares)	(1,925)	(1,685)	(979)	(856)	(1,685)	(856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of shares	(457)	(240)	(113)	(123)
Balance at end of period (in shares)	(2,382)	(1,925)	(1,092)	(979)	(2,382)	(1,092)
Treasury Stock | Class B
Balance at beginning of period (in shares)	(3,101)	(2,656)	(2,176)	(2,147)	(2,656)	(2,147)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares withheld related to net settlement of equity awards	(43)	(445)	(8)	(29)
Balance at end of period (in shares)	(3,144)	(3,101)	(2,184)	(2,176)	(3,144)	(2,184)