Stockholders' Equity - Components and Voting Power of Outstanding Common Stock (Detail) - shares	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common Stock Outstanding (in shares)	119,425,957
Percentage	100.00%
Common Class A [Member]
Class of Stock [Line Items]
Common Stock Outstanding (in shares)	30,415,653	32,224,421
Percentage	25.50%
Common Class B [Member]
Class of Stock [Line Items]
Common Stock Outstanding (in shares)	89,010,304	89,108,569
Percentage	74.50%