Long-Term Target Allocations of Assets for US And UK Plans (Detail)	12 Months Ended
	Dec. 31, 2012
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	100.00%
U.S. Plans | Equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	60.00%
U.S. Plans | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	38.00%
U.S. Plans | Real Estate And Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	2.00%
United Kingdom Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	100.00%
United Kingdom Plan | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	4.00%
United Kingdom Plan | Equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	50.00%
United Kingdom Plan | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	26.00%
United Kingdom Plan | Real Estate And Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan target plan asset allocations	20.00%