Financial Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	$ 20,483	[1]	$ 20,265	[1]
Equity securities	22	[2]	25	[2]
Foreign currency forward contracts, assets	251	[3]	262	[3]
Obligations under executive deferred compensation plan	20,483	[1]	20,265	[1]
Foreign currency forward contracts, liabilities	13	[3]	771	[3]
Quoted Prices in Active Markets for Identical Items (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	20,483	[1]	20,265	[1]
Equity securities	22	[2]	25	[2]
Foreign currency forward contracts, assets		[3]		[3]
Obligations under executive deferred compensation plan	20,483	[1]	20,265	[1]
Foreign currency forward contracts, liabilities		[3]		[3]
Quoted Prices in Active Markets for Similar Items (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan		[1]		[1]
Equity securities		[2]		[2]
Foreign currency forward contracts, assets	251	[3]	262	[3]
Obligations under executive deferred compensation plan		[1]		[1]
Foreign currency forward contracts, liabilities	$ 13	[3]	$ 771	[3]

[1] We maintain an Executive Deferred Compensation Plan (EDCP) that was adopted in 2001 and subsequently amended. The purpose of the EDCP is to provide current tax planning opportunities as well as supplemental funds upon the retirement or death of certain of our employees. The EDCP is intended to aid in attracting and retaining employees of exceptional ability by providing them with these benefits. We also maintain a Benefit Protection Trust (the Trust) that was created to provide a source of funds to assist in meeting the obligations of the EDCP, subject to the claims of our creditors in the event of our insolvency. Assets of the Trust are consolidated in accordance with authoritative guidance. The assets of the Trust consist primarily of mutual fund investments (which are accounted for as trading securities and are marked-to-market on a monthly basis through the consolidated statements of income) and cash and cash equivalents. As such, these assets and obligations are classified within Level 1.

[2] Our investments in equity securities are classified as available-for-sale and are reported in Investments in the condensed consolidated balance sheets. The changes in fair value are reported in Other in our consolidated statements of comprehensive income. These securities are classified within Level 1.

[3] As a result of our global operating and financing activities, we are exposed to market risks from changes in interest and foreign currency exchange rates, which may adversely affect our operating results and financial position. When deemed appropriate, we minimize our risks from interest and foreign currency exchange rate fluctuations through the use of derivative financial instruments. The foreign currency forward contracts are valued using broker quotations or market transactions in either the listed or over-the-counter markets. As such, these derivative instruments are classified within Level 2.