Pension and Other Postretirement Benefits - Schedule of Changes in Plan Assets (Detail) £ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2019 GBP (£)	Dec. 31, 2018 USD ($)
Foreign Pension Benefits [Member]
Change in plan assets:
Fair value of plan assets, Beginning balance	$ 49,651	£ 38,991
Corporate contributions			$ 982
Fair value of plan assets, Ending balance	57,900	£ 43,913	49,651
Defined Benefit Pension Plan [Member] | U.S. [Member]
Change in plan assets:
Fair value of plan assets, Beginning balance	182,541		199,138
Actual return on plan assets	26,304		(4,765)
Foreign currency exchange rate changes	0		0
Corporate contributions	1,660		1,614
Participant contributions	0		0
Gross benefits paid	(14,838)		(13,446)
Fair value of plan assets, Ending balance	195,667		182,541
Defined Benefit Pension Plan [Member] | Foreign Pension Benefits [Member]
Change in plan assets:
Fair value of plan assets, Beginning balance	49,651		56,419
Actual return on plan assets	8,164		(2,477)
Foreign currency exchange rate changes	1,964		(2,991)
Corporate contributions	656		1,648
Participant contributions	0		0
Gross benefits paid	(2,535)		(2,948)
Fair value of plan assets, Ending balance	57,900		49,651
Other Postretirement Benefit Plans [Member]
Change in plan assets:
Fair value of plan assets, Beginning balance	0		0
Actual return on plan assets	0		0
Foreign currency exchange rate changes	0		0
Corporate contributions	1,228		1,103
Participant contributions	99		104
Gross benefits paid	(1,327)		(1,207)
Fair value of plan assets, Ending balance	$ 0		$ 0