Stock Compensation Plans - RSU, PRS and Cash RSU Activity (Detail) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Weighted Average Grant Date Fair Value Per Share	$ 10.39	$ 11.47	$ 10.41
RSU's [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at December 31, 2011, Number of Shares	782,000
Granted, Number of Shares	211,000
Vested, Number of Shares	(333,000)
Forfeited/Cancelled, Number of Shares	(41,000)
Balance at December 31, 2012, Number of Shares	619,000
Balance at December 31, 2011, Weighted Average Grant Date Fair Value Per Share	$ 44.91
Granted, Weighted Average Grant Date Fair Value Per Share	$ 56.43
Vested, Weighted Average Grant Date Fair Value Per Share	$ 30.24
Forfeited/Cancelled, Weighted Average Grant Date Fair Value Per Share	$ 47.30
Balance at December 31, 2012, Weighted Average Grant Date Fair Value Per Share	$ 54.09
PRS [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at December 31, 2011, Number of Shares	497,000
Granted, Number of Shares	228,750	174,212	213,714
Vested, Number of Shares	(159,000)
Forfeited/Cancelled, Number of Shares	(30,000)
Balance at December 31, 2012, Number of Shares	537,000	497,000
Balance at December 31, 2011, Weighted Average Grant Date Fair Value Per Share	$ 23.03
Granted, Weighted Average Grant Date Fair Value Per Share	$ 30.20
Vested, Weighted Average Grant Date Fair Value Per Share	$ 15.51
Forfeited/Cancelled, Weighted Average Grant Date Fair Value Per Share	$ 23.35
Balance at December 31, 2012, Weighted Average Grant Date Fair Value Per Share	$ 28.30	$ 23.03
Cash RSU's [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at December 31, 2011, Number of Shares	154,000
Granted, Number of Shares	42,000
Vested, Number of Shares	(64,000)
Forfeited/Cancelled, Number of Shares	(12,000)
Balance at December 31, 2012, Number of Shares	120,000
Balance at December 31, 2011, Weighted Average Grant Date Fair Value Per Share	$ 52.42
Granted, Weighted Average Grant Date Fair Value Per Share	$ 65.96
Vested, Weighted Average Grant Date Fair Value Per Share	$ 60.21
Forfeited/Cancelled, Weighted Average Grant Date Fair Value Per Share	$ 57.79
Balance at December 31, 2012, Weighted Average Grant Date Fair Value Per Share	$ 65.96

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

+ Details

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- Definition

The number of grants made 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).

+ References

+ Details

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- Definition

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).

+ 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)(2)(iii)(1)

-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 c(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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(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.

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ 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)(2)(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(2)(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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-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.

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ 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)(2)(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(2)(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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-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 number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

+ Details

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

+ Details

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