Stock Option Plan and Stock Grants - Additional Information (Detail) (USD $)	6 Months Ended	1 Months Ended
Jun. 30, 2011	Jun. 30, 2010	May 11, 2011 Restricted Stock Directors Plan	Jan. 31, 2011 Restricted Stock Directors Plan	Feb. 01, 2011 Restricted Stock Senior Management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amortization of stock-related compensation	$ 2,969,000	$ 2,465,000
Common stock exercised shares	12,000	20,250
Proceeds from stock options exercised	200,000	900,000
Share based compensation, grants awarded			16,000	31,000	72,665
Share based compensation, vesting date					2011-12-31
Share based compensation, fair market value			$ 900,000	$ 1,800,000	$ 4,200,000
Share based compensation, vesting description			One-third of the shares of restricted common stock covered by these awards vests on each of November 11, 2011, May 11, 2012, and May 11, 2013.	One-third of the shares of restricted common stock covered by these awards vests on each of December 31, 2011, December 31, 2012, and December 31, 2013.

The total fair value of shares issued during the period under a deferred compensation arrangement.

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph i
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3255-108585

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 18
-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 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 19
-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.

+ Details

- Definition

Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

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- Definition

Number of share options (or share units) exercised during the current period.

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