Leases - Summary of Future Minimum Lease Payments For Noncancelable Operating And Financing Leases (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Dec. 30, 2018
Lessee Disclosure [Line Items]
Operating Leases, Remainder of 2019	$ 12,426
Operating Leases, 2020	16,444
Operating Leases, 2021	14,251
Operating Leases, 2022	11,636
Operating Leases, 2023	10,050
Operating Leases, Thereafter	34,245
Total operating leases including interest	99,052
Less: Amounts representing interest	14,152
Present value of minimum lease principal payments	84,900	$ 88,200
Less: Current portion of lease liabilities - operating leases	13,555
Noncurrent portion of lease liabilities - operating leases	71,345
Financing Leases, Remainder of 2019	7,830
Financing Leases, 2020	10,611
Financing Leases, 2021	6,215
Financing Leases, 2022	2,694
Financing Leases, 2023	2,750
Financing Leases, Thereafter	8,214
Total financing leases including interest	38,314
Less: Amounts representing interest	4,966
Present value of minimum lease principal payments	33,348
Less: Current portion of lease liabilities - financing leases	8,833		$ 8,617
Noncurrent portion of lease liabilities - financing leases	24,515		$ 26,631
Total Operating and Financing Leases [Member]
Lessee Disclosure [Line Items]
Total future minimum payments due remainder of 2019	20,256
Total future minimum payments due in 2020	27,055
Total future minimum payments due in 2021	20,466
Total future minimum payments due in 2022	14,330
Total future minimum payments due in 2023	12,800
Total future minimum payments due, in Thereafter	42,459
Total minimum lease payments including interest	137,366
Less: Amounts representing interest	19,118
Present value of minimum lease principal payments	118,248
Less: Current portion of lease liabilities - operating and financing leases	22,388
Noncurrent portion of lease liabilities - operating and financing leases	$ 95,860