Class A Redeemable Convertible Preferred Stock (Detail) - USD ($)				3 Months Ended	12 Months Ended
	Jun. 25, 2018	Jun. 24, 2018	Dec. 22, 2016	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 30, 2015
Temporary Equity [Line Items]
Payments for Repurchase of Redeemable Preferred Stock					$ 0	$ 50,096,000	$ 0
Gain on redemption of preferred stock				$ 9,100,000	$ 0	$ 9,075,000	$ 0
Series A Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock, shares issued									14,666,667
Preferred stock, par value			$ 7,500,000						$ 7.50
Preferred stock, liquidation preference			$ 49,500,000						$ 110,000,000.0
Preferred stock, liquidation amount at redemption								$ 100,000,000.0
Preferred stock, shares redeemed			8,066,667
Preferred stock, redemption amount			$ 55,000,000.0
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	6,864,000	6,600,000
Payments for Repurchase of Redeemable Preferred Stock	$ 50,100,000
Preferred stock, redemption price, accrued and unpaid dividends, addition price per share	$ 0.14
Preferred stock, carrying amount attributable to parent		$ 37,800,000
Preferred stock, recognized amount of beneficial conversion feature		$ 21,300,000
Temporary equity, par value (in dollars per share)			$ 32,900,000						$ 73,200,000
Shares issued (in dollars per share)									$ 4.99
Preferred stock, issue discount			16,600,000						$ 36,800,000
Preferred stock, beneficial conversion feature			$ 20,100,000						$ 44,700,000
Series A Redeemable Convertible Preferred Stock | Payment In Kind
Temporary Equity [Line Items]
Preferred stock, shares issued							264,000