Stock-Based Option Grants - Additional Information (Detail) (Employee Stock Compensation Plan, USD $)	1 Months Ended
Feb. 29, 2012	Jan. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period	24,000	18,600
Options granted in period, weighted average fair value	$ 41.64	$ 47.55
Percentage of shares vesting on January 1, 2017	33.00%
Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period		7,500
Percentage of shares vesting on January 1, 2017		60.00%
Vesting period		4 years

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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

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Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration