Summary of Basis Used to Measure Defined Benefit Plans Assets at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	$ 76,141		$ 94,238
Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	14,968	[1]	19,779	[1]
United States Absolute Return Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	38,449	[1]	45,555	[1]
Non United States Absolute Return Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	21,709	[1]	26,685	[1]
Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets			2,219	[2]
Defined benefit plan, fair value of plan assets	1,015	[2]
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	70,952		86,451
Fair Value, Inputs, Level 1 | Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	14,968	[1]	19,779	[1]
Fair Value, Inputs, Level 1 | United States Absolute Return Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	38,449	[1]	45,555	[1]
Fair Value, Inputs, Level 1 | Non United States Absolute Return Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	16,520	[1]	18,898	[1]
Fair Value, Inputs, Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets			2,219	[2]
Defined benefit plan, fair value of plan assets	1,015	[2]
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	5,189		7,787
Fair Value, Inputs, Level 2 | Non United States Absolute Return Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	$ 5,189	[1]	$ 7,787	[1]

[1] Primarily funds invested by managers that have a global mandate with the flexibility to allocate capital broadly across a wide range of asset classes and strategies including, but not limited to equities, fixed income, commodities, interest rate futures, currencies and other securities to outperform an agreed benchmark with specific return and volatility targets.

[2] Primarily cash and cash equivalents.