Borrowings (Detail)			12 Months Ended
	Oct. 01, 2018 USD ($) $ / shares	Nov. 21, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 02, 2018 USD ($)
Credit Facilities [Line Items]
Current portion of long-term borrowings			$ 40,867,000	$ 21,423,000
Long-term borrowings, less current portion			194,131,000	263,241,000
Debt offering expense			117,000	762,000	$ 790,000
Allocation of equity component related to the convertible senior notes, net of tax and issuance costs			(13,000)	12,555,000
Amortization of non-cash interest expense related to convertible senior notes			2,472,000	0	$ 0
Structured payable			249,867,000
Outstanding letters of credit			461,000	0
Structured Payables
Credit Facilities [Line Items]
Current portion of long-term borrowings			867,000	1,423,000
Long-term borrowings, less current portion			0	691,000
Structured payable			867,000	2,114,000
3.50% Convertible Senior Notes due October 1, 2024 | Notes
Credit Facilities [Line Items]
Debt instrument face amount	$ 150,000,000
Interest rate	3.50%
Interest expense			5,206,000	1,313,000
Conversion rate	0.0133333
Conversion price (in dollars per share) | $ / shares	$ 75
Threshold percentage of stock price trigger	150.00%
Net proceeds from convertible notes	$ 149,000,000
Debt issuance costs	1,000,000
Debt offering expense	442,000
Liability component of debt issuance costs	1,279,000
Equity component of debt issuance costs	163,000
Unamortized debit issuance costs			$ 1,018,000	1,127,000
Convertible notes, liability component	133,077,000
Convertible senior notes, interest rate			5.75%
Allocation of equity component related to the convertible senior notes, net of tax and issuance costs	$ 16,923,000
Debt instrument, convertible, remaining discount amortization period	6 years
Amortization of non-cash interest expense related to convertible senior notes			$ 2,472,000	600,000
Unamortized debt discount			13,851,000	16,323,000
Structured payable			150,000,000	150,000
Revolver Credit
Credit Facilities [Line Items]
Revolving credit facility			99,000,000	150,000,000
Current portion of long-term borrowings			40,000,000	20,000,000
Long-term borrowings, less current portion			59,000,000	130,000,000
Unamortized debt issuance costs			748,000	$ 1,006,000
Repayments of credit facility	$ 150,000,000
Structured payable			$ 99,000,000
Revolver Credit | Credit Agreement
Credit Facilities [Line Items]
Revolving credit facility		$ 200,000,000
Option to increase additional credit facility		$ 100,000				$ 100,000,000
Line of credit , maximum borrowing capacity						$ 300,000,000
Line of credit interest rate during period			4.00%	3.40%
Unrestricted domestic cash and cash equivalents			$ 50,000,000
Interest coverage ratio, minimum		3.5
Interest coverage ratio, maximum		3.0
Revolver Credit | Credit Agreement | Minimum
Credit Facilities [Line Items]
Commitment fee percentage range on unused credit facility		0.15%
Revolver Credit | Credit Agreement | Maximum
Credit Facilities [Line Items]
Commitment fee percentage range on unused credit facility		0.30%
Revolver Credit | Credit Agreement | Prime Rate | Minimum
Credit Facilities [Line Items]
Basis spread on variable rate		0.00%
Revolver Credit | Credit Agreement | Prime Rate | Maximum
Credit Facilities [Line Items]
Basis spread on variable rate		0.75%
Revolver Credit | Credit Agreement | London Interbank Offered Rate (LIBOR) | Minimum
Credit Facilities [Line Items]
Basis spread on variable rate		1.00%
Revolver Credit | Credit Agreement | London Interbank Offered Rate (LIBOR) | Maximum
Credit Facilities [Line Items]
Basis spread on variable rate		1.75%