Employee Benefit Plans - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016 USD ($)	Dec. 31, 2016 GBP (£)	Dec. 31, 2016 Rate	Dec. 31, 2015 USD ($) Rate	Dec. 31, 2014 USD ($)
Pension and Other Postretirement Benefits Disclosure
Health Care Cost Trend Rate Assumed for Next Fiscal Year | Rate					7.00%	7.50%
Ultimate Health Care Cost Trend Rate | Rate					5.00%
Effect of One Percentage Point Increase on Service and Interest Cost Components			$ 200,000
Effect of One Percentage Point Decrease on Service and Interest Cost Components			(200,000)
Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation			900,000
Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation			(800,000)
Future Amortization of Actuarial Gain (Loss)			20,200,000
Future Amortization of Prior Service Cost (Credit)			700,000
Pension Benefits, U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Expected Long-term Return on Assets Assumptions Used Calculating Net Periodic Benefit Cost		7.50%				7.50%
Plan Amendments			0			$ 7,500,000
Pension Plan Lump-sum Settlement Payment							$ 214,500,000
Pension Settlement Costs			0			$ 0	64,400,000
Average Remaining Life Expectancy of Plan Participants	25 years
General Discussion of Pension and Other Postretirement Benefits	We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2016
Pension Benefits, Non U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Expected Long-term Return on Assets Assumptions Used Calculating Net Periodic Benefit Cost		4.90%				5.20%
Plan Amendments			0			$ 0
Pension Settlement Costs			0			$ 0	0
Average Remaining Life Expectancy of Plan Participants	33 years
Pension Contributions			0
Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure
Expected Long-term Return on Assets Assumptions Used Calculating Net Periodic Benefit Cost		5.75%			5.75%	5.75%
Plan Amendments			3,700,000			$ 0
Pension Settlement Costs			0			0	0
Level 3 Transfers Into			0			0
Level 3 Transfers Out of			0			$ 0
Interest Rate During Period		4.99%				5.24%
Health Care Cost Trend Rate Assumed for Next Fiscal Year | Rate						7.50%
Diversified Growth Assets | Pension Benefits, Non U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Target Plan Asset Allocations | Rate					65.00%
Equity Securities | Pension Benefits, U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Target Plan Asset Allocations | Rate					33.00%
Interest Rate Contract | Pension Benefits, Non U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Target Plan Asset Allocations | Rate					35.00%
Fixed Maturity Securities | Pension Benefits, U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Target Plan Asset Allocations | Rate					40.00%
Alternative Investments | Pension Benefits, U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Target Plan Asset Allocations | Rate					27.00%
Minimum
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	1 year
Minimum | Private Equity Funds | Pension Benefits, U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	5 years
Maximum
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	11 years
Maximum | Private Equity Funds | Pension Benefits, U.S. Plans
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	8 years
U.S. Defined Contribution Plan
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay | Rate					5.00%
Employer Discretionary Contribution Percentage of earnings | Rate					4.50%
Cost Recognized			72,200,000.0			$ 71,500,000.0	$ 76,000,000
Non U.S. Defined Contribution Plan
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay		5.00%					5.00%
Employer Discretionary Contribution Percentage of earnings		6.00%					5.00%
Employer Matching Contribution for Every Pound on the First One Percent of Employee Contributions | £				£ 2
Employee Contribution Percentage Received 2-for-1 Employer Match		1.00%
Cost Recognized			$ 4,900,000.0			$ 5,700,000.0	$ 5,000,000