Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2012 Y	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Minimum eligible age for employees to defer a portion of their compensation, years	21
Contribution made by company to match employee contribution	$ 0.375	$ 0.375	$ 0.750
Employee contribution eligible for employer matching program	1.00	1.00	1.00
Maximum employer matching contribution, salary percentage	6.00%	6.00%	6.00%
Expense made by company	$ 10,000,000	$ 7,400,000	$ 22,200,000
Permitted deferment of compensation, percentage	75.00%
Permitted deferment of annual bonus, percentage	100.00%

Deferred compensation arrangement maximum percentage of annual bonus deferment.

No definition available.

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- Definition

Defined Contribution Plan Employee Contribution For Employer Matching Program

+ References

No definition available.

+ Details

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- Definition

Defined contribution plan employer matching contribution.

+ References

No definition available.

+ Details

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- Definition

Defined Contribution Plan Maximum Annual Matching Program Per Employee Salary Percentage

+ References

No definition available.

+ Details

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- Definition

Minimum eligible age for employees to defer a portion of their compensation.

+ References

No definition available.

+ Details

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- Details

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Maximum percentage of employee gross pay, by the terms of the plan, that the employer may contribute to a defined contribution plan.

+ References

No definition available.

+ Details

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