Stock Compensation Plans - SSAR's and Stock Option Outstanding (Detail) (SSAR's and Stock Options [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	606
Weighted Average Exercise Price	$ 44.68
Aggregate Intrinsic Value	$ 12,888
$26 - $30 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	78
Price Range, lower limit	$ 26
Price Range, upper limit	$ 30
Weighted Average Remaining Contractual Life (in years)	3 years 4 months 24 days
Weighted Average Exercise Price	$ 30.19
$31 - $35 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	72
Price Range, lower limit	$ 31
Price Range, upper limit	$ 35
Weighted Average Remaining Contractual Life (in years)	1 year 4 months 24 days
Weighted Average Exercise Price	$ 33.78
$36 - $40 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	74
Price Range, lower limit	$ 36
Price Range, upper limit	$ 40
Weighted Average Remaining Contractual Life (in years)	2 years 9 months 18 days
Weighted Average Exercise Price	$ 36.87
$41 - $50 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	199
Price Range, lower limit	$ 41
Price Range, upper limit	$ 50
Weighted Average Remaining Contractual Life (in years)	4 years
Weighted Average Exercise Price	$ 44.30
$51 - $55 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	51
Price Range, lower limit	$ 51
Price Range, upper limit	$ 55
Weighted Average Remaining Contractual Life (in years)	3 years 10 months 24 days
Weighted Average Exercise Price	$ 51.44
$56 - $65 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	132
Price Range, lower limit	$ 56
Price Range, upper limit	$ 65
Weighted Average Remaining Contractual Life (in years)	5 years 9 months 18 days
Weighted Average Exercise Price	$ 61.42

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph d(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(a, b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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- Definition

The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

+ References

+ Details

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- Definition

Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

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- Definition

The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

+ Details

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