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Capitalization - Secondary Offering (Detail) - Class A common stock - Secondary Offering - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Jun. 30, 2017	Mar. 31, 2017
Class of Stock [Line Items]
Number of shares sold by selling shareholders net of option granted to underwriters	4,846,600	7,281,789
Secondary offering price	$ 52.00	$ 35.50
Additional shares sold under option granted to underwriters	530,148	949,798
Offering costs incurred	$ 0.6	$ 0.9

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