Plans Fair Value of Plan Assets by Asset Class (Detail) - USD ($) $ in Thousands		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		$ 370,497		$ 378,194
Short Term Investments And Cash
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		5,200		6,701
Equity Securities | Domestic Equity Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[1]	54,949		63,551
Equity Securities | Us Companies
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		93,600		94,739
Equity Securities | International Companies
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		1,957		2,700
Equity Securities | International Equity Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[2]	53,971		45,851
Fixed Income Securities | US Treasury Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		5,257		4,664
Fixed Income Securities | US Government Agencies Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		3,215		874
Fixed Income Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		7,201		2,333
Fixed Income Securities | Domestic Corporate Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		2,787		2,452
Real Estate Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[3]	17,336		14,651
Hedge Funds, Equity
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		500		14,300
Other Assets And Liabilities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[4]	183		184
Accrued (Expenses) Income
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[4]	(375)		(470)
Other Investments | Guaranteed Insurance Contracts
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[5]	9,784		9,450
Other Investments | Hedge Funds, Equity
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[7]	40,582	[6]	52,420	[8]
Other Investments | Absolute Return Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[9]	74,850		78,094	[10]
Level 1
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		150,506		160,990
Level 1 | Equity Securities | Domestic Equity Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[1]	54,949		63,551
Level 1 | Equity Securities | Us Companies
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		93,600		94,739
Level 1 | Equity Securities | International Companies
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		1,957		2,700
Level 2
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		77,631		62,875
Level 2 | Short Term Investments And Cash
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		5,200		6,701
Level 2 | Equity Securities | International Equity Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[2]	53,971		45,851
Level 2 | Fixed Income Securities | US Treasury Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		5,257		4,664
Level 2 | Fixed Income Securities | US Government Agencies Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		3,215		874
Level 2 | Fixed Income Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		7,201		2,333
Level 2 | Fixed Income Securities | Domestic Corporate Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		2,787		2,452
Level 3
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		142,360		154,329		$ 161,578
Level 3 | Guaranteed Insurance Contracts
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		9,784		9,450		9,594
Level 3 | Real Estate Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		17,336	[3]	14,651	[3]	13,298
Level 3 | Hedge Funds, Equity
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets		40,582		52,420		$ 58,176
Level 3 | Other Assets And Liabilities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[4]	183		184
Level 3 | Accrued (Expenses) Income
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[4]	(375)		(470)
Level 3 | Other Investments | Guaranteed Insurance Contracts
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[5]	9,784		9,450
Level 3 | Other Investments | Hedge Funds, Equity
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[7]	40,582	[6]	52,420	[8]
Level 3 | Other Investments | Absolute Return Funds
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets	[9]	$ 74,850		$ 78,094	[10]

[1] There is a pending sale for an asset in this classification.

[2] This class includes funds with the principal strategy to invest primarily in long positions in international equity securities.

[3] This class includes funds that invest primarily in U.S. commercial real estate.

[4] This class includes accrued interest, dividends, and amounts receivable from asset sales and amounts payable for asset purchases.

[5] This class invests primarily guaranteed insurance contracts through various U.S. insurance companies.

[6] Pending sale requests of $0.5 million apply to assets reported in this classification.

[7] This class invests primarily in hedged equity funds.

[8] Pending sale requests of $14.3 million apply to assets reported in this classification.

[9] This class invests primarily in absolute return strategy funds.

[10] Pending sale requests of $8.0 million apply to assets reported in this classification.