Class A Redeemable Convertible Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Jun. 25, 2018	Jun. 24, 2018	Dec. 22, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 30, 2015
Temporary Equity [Line Items]
Redemption of preferred stock				$ 0	$ 0	$ 50,096
Gain on redemption of preferred stock	$ 9,100			$ 0	$ 0	$ 9,075
Series A Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock, shares issued									14,666,667
Preferred stock, par value (in dollars per share)			$ 7,500,000						$ 7.50
Preferred stock, liquidation preference									$ 110,000
Preferred stock, shares, redemption			8,066,667
Preferred stock, redemption amount			$ 55,000
Preferred stock redemption price per share (in dollars per share)	$ 7.30		$ 6,820,000
Preferred stock, redemption discount	4.55%		9.09%
Preferred stock, shares outstanding				0	0	0	6,864,000
Redemption of preferred stock	$ 50,100
Preferred stock, redemption price, accrued and unpaid dividends, addition price per share	$ 0.14
Preferred stock, carrying amount attributable to parent		$ 37,800
Preferred stock, recognized amount of beneficial conversion feature		$ 21,300
Preferred stock, liquidation amount at redemption								$ 100,000
Series A Redeemable Convertible Preferred Stock | Payment In Kind
Temporary Equity [Line Items]
Preferred stock, shares issued							264,000