Benefit Plans - Stock Options Outstanding (Detail) (USD $)	12 Months Ended
Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Options Outstanding	2,860,081
Weighted Average Remaining Contractual Life in Years	3 years 2 months 12 days
Weighted Average Exercise Price	$ 17
Number of Options Exercisable	2,756,007
Weighted Average Exercise Price	$ 18
Range of Exercise Prices 10 - 15 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 10
Range of Exercise Prices, Upper Range Limit	$ 14
Number of Options Outstanding	193,364
Weighted Average Remaining Contractual Life in Years	6 years 1 month 6 days
Weighted Average Exercise Price	$ 12
Number of Options Exercisable	136,741
Weighted Average Exercise Price	$ 12
Range of Exercise Prices 15 - 16 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 14
Range of Exercise Prices, Upper Range Limit	$ 15
Number of Options Outstanding	472,094
Weighted Average Remaining Contractual Life in Years	5 years 2 months 12 days
Weighted Average Exercise Price	$ 15
Number of Options Exercisable	425,457
Weighted Average Exercise Price	$ 15
Range of Exercise Prices 16 - 18 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 15
Range of Exercise Prices, Upper Range Limit	$ 17
Number of Options Outstanding	195,991
Weighted Average Remaining Contractual Life in Years	3 years 7 months 6 days
Weighted Average Exercise Price	$ 17
Number of Options Exercisable	195,261
Weighted Average Exercise Price	$ 17
Range of Exercise Prices 18 - 19 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 17
Range of Exercise Prices, Upper Range Limit	$ 18
Number of Options Outstanding	511,651
Weighted Average Remaining Contractual Life in Years	2 years 10 months 24 days
Weighted Average Exercise Price	$ 18
Number of Options Exercisable	511,604
Weighted Average Exercise Price	$ 18
Range of Exercise Prices 19 - 21 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 18
Range of Exercise Prices, Upper Range Limit	$ 21
Number of Options Outstanding	1,486,981
Weighted Average Remaining Contractual Life in Years	2 years 2 months 12 days
Weighted Average Exercise Price	$ 19
Number of Options Exercisable	1,486,944
Weighted Average Exercise Price	$ 19

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

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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 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

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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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