Activity Related to Liability for Special Charges (Parenthetical) (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017		Dec. 31, 2016
Other Income And Expenses [Abstract]
Special charges remaining liability	$ 40,750	[1]	$ 11,560
Total expected payments to special charges, amount expected to be paid in 2017	16,900
Total expected payments to special charges, amount expected to be paid in 2018	10,500
Total expected payments to special charges, amount expected to be paid in 2019	4,900
Total expected payments to special charges, amount expected to be paid in 2020	4,100
Total expected payments to special charges, amount expected to be paid from 2021 to 2025	$ 4,400

[1] Of the $40.8 million remaining liability for the special charges, $16.9 million is expected to be paid in the remainder of 2017, $10.5 million is expected to be paid in 2018, $4.9 million is expected to be paid in 2019, $4.1 million is expected to be paid in 2020 and the remaining balance of $4.4 million is expected to be paid from 2021 to 2025.