Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2012 Age	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock options granted	71,686
Non-qualified stock options received by nonemployee directors	3,000
Weighted-average grant-date exercise price of options granted	$ 69.12	$ 86.90	$ 95.27
Aggregate intrinsic values of options exercised	$ 7,176,000	$ 1,621,000	$ 3,978,000
Aggregate intrinsic values for options outstanding	13,121,000
Aggregate intrinsic values for options exercisable	10,492,000
Common stock price	$ 94.28
Percentage of incentive compensation to acquire shares, maximum	50.00%
Percentage of discount rate to market value on the incentive compensation	20.00%
Company normal retirement age	62
Shares available for grant	510,000
Common stock reserved for future issuance	250,000
Cumulative shares issued under shareholder value achievement plan	42,025
Recognized tax benefit related to stock-based compensation expense	3,075,000	4,557,000	5,804,000
Incentive Compensation Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock price	$ 94.28
Weighted-average grant-date fair value of stock awards, granted	$ 81.41	$ 84.71	$ 79.78
Aggregate intrinsic values for stock awards	808,000
Aggregate intrinsic values of stock awards, distributed	375,000	165,000	0
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value of stock awards, granted	$ 69.12	$ 86.90	$ 91.33
Aggregate intrinsic values for stock awards	22,495,000
Aggregate intrinsic values of stock awards, distributed	$ 8,695,000	$ 10,237,000	$ 10,031,000
Directors' Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	300,000
Minimum percentage of directors retainer required to be paid in common stock	50.00%
Percentage of discount rate to market value on directors fees paid in common stock	20.00%
Common stock issued under the plan	23,830	19,977	17,804

Common stock price.

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Company normal retirement age.

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Cumulative shares issued under shareholder value achievement plan.

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Minimum percentage of directors retainer required to be paid in common stock.

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Non-Qualified Stock Options Received By Non-Employee Directors

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Percentage of discount rate to market value on directors fees paid in common stock.

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Percentage Of Discount Rate To The Market Value On The Incentive Compensation

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Percentage Of Incentive Compensation To Acquire Shares Maximum

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Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested In Period Total Intrinsic Value

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Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Intrinsic Value

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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Net number of share options (or share units) granted during the period.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of options outstanding.

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Number of share instruments newly issued under a share-based compensation plan.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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