Stock Compensation Plans - SSAR's and Stock Option Exercisable (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 Exercisable	320
Exercise Price	$ 37.64
Aggregate Intrinsic Value	$ 9,051
$26 - $30 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price Range, lower limit	$ 26
Price Range, upper limit	$ 30
Number Exercisable	78
Contractual Life (in years)	3 years 4 months 24 days
Exercise Price	$ 30.19
$31 - $35 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price Range, lower limit	$ 31
Price Range, upper limit	$ 35
Number Exercisable	72
Contractual Life (in years)	1 year 4 months 24 days
Exercise Price	$ 33.78
$36 - $40 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price Range, lower limit	$ 36
Price Range, upper limit	$ 40
Number Exercisable	74
Contractual Life (in years)	2 years 9 months 18 days
Exercise Price	$ 36.87
$41 - $50 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price Range, lower limit	$ 41
Price Range, upper limit	$ 50
Number Exercisable	45
Contractual Life (in years)	2 years 3 months 18 days
Exercise Price	$ 42.18
$51 - $55 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price Range, lower limit	$ 51
Price Range, upper limit	$ 55
Number Exercisable	51
Contractual Life (in years)	3 years 10 months 24 days
Exercise Price	$ 51.44

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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.

+ 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

+ Details

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- Definition

Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and 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

-Subparagraph (c)(1)(iii)

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

+ Details

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- Definition

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

+ 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 (e)(2)

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

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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

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- Definition

The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

-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 (c)(iii)

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

+ 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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