Postretirement Benefit Plans - Company's Asset Allocations for its U.K. Pension Plans by Asset Category (Detail) - United Kingdom [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total	$ 24,357	$ 20,576	$ 24,168
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	252	205
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	22,900	19,128
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,205	1,243
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,372	205
Cash [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	252	205
Cash [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,120
Pooled Pension Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,533	12,750
Pooled Pension Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,533	12,750
Pooled Fixed Pension Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	14,247	6,378
Pooled Fixed Pension Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	14,247	6,378
Insurance Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,205	1,243
Insurance Contracts [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 1,205	$ 1,243