Future Minimum Rental Payments under Lease Commitments (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Leases [Abstract]
Capital Leases, 2018	$ 3,899
Capital Leases, 2019	4,003
Capital Leases, 2020	3,345
Capital Leases, 2021	3,227
Capital Leases, 2022	3,508
Capital Leases, Later years	15,694
Capital Leases, Total minimum rental	33,676
Less: Amount representing interest	(11,891)
Present value of minimum rental commitments	21,785
Less: Current portion of capital lease obligations	(1,837)
Long-term portion of capital lease obligations	19,948
Operating Leases, 2018	73,310
Operating Leases, 2019	63,156
Operating Leases, 2020	50,948
Operating Leases, 2021	42,167
Operating Leases, 2022	24,871
Operating Leases, Later years	147,965
Operating Leases, Total minimum rental	$ 402,417