Plan Assets Using Fair Value Hierarchy (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 419,771	$ 385,483
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,084	13,803
Fixed Income Securities | Foreign Government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	76,196	42,828
Fixed Income Securities | US Treasury Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	82,989	60,710
Fixed Income Securities | Collateralized Mortgage Backed Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40,915	31,420
Fixed Income Securities | Others
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,177	6,943
Equity Securities | US Small Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,094	7,982
Equity Securities | US Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,532	8,811
Equity Securities | US Large Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47,398	45,700
Equity Securities | International Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	39,594	45,859
Equity Securities | US Long Short Equity Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	56,575	56,639
Equity Securities | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,645	18,255
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23,572	46,533
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51,209	59,012
Fair Value, Inputs, Level 1 | Equity Securities | US Small Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,094	7,982
Fair Value, Inputs, Level 1 | Equity Securities | US Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,528	8,811
Fair Value, Inputs, Level 1 | Equity Securities | International Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,942	23,964
Fair Value, Inputs, Level 1 | Equity Securities | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,645	18,255
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	348,555	311,703
Fair Value, Inputs, Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,084	13,803
Fair Value, Inputs, Level 2 | Fixed Income Securities | Foreign Government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	76,046	42,544
Fair Value, Inputs, Level 2 | Fixed Income Securities | US Treasury Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	82,989	60,710
Fair Value, Inputs, Level 2 | Fixed Income Securities | Collateralized Mortgage Backed Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40,286	30,052
Fair Value, Inputs, Level 2 | Fixed Income Securities | Others
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,958	6,818
Fair Value, Inputs, Level 2 | Equity Securities | US Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4
Fair Value, Inputs, Level 2 | Equity Securities | US Large Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47,398	45,700
Fair Value, Inputs, Level 2 | Equity Securities | International Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,652	21,895
Fair Value, Inputs, Level 2 | Equity Securities | US Long Short Equity Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	56,575	56,639
Fair Value, Inputs, Level 2 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,563	33,542
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20,007	14,768
Fair Value, Inputs, Level 3 | Fixed Income Securities | Foreign Government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	150	284
Fair Value, Inputs, Level 3 | Fixed Income Securities | Collateralized Mortgage Backed Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	629	1,368
Fair Value, Inputs, Level 3 | Fixed Income Securities | Others
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	219	125
Fair Value, Inputs, Level 3 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 19,009	$ 12,991