Investments (Details) (USD $) In Thousands	6 Months Ended	0 Months Ended		0 Months Ended	6 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Apr. 15, 2011 Held-To-Maturity Investment Maturing On October 17, 2011 [Member]	Jun. 30, 2011 Held-To-Maturity Investment Maturing On October 17, 2011 [Member]	Jan. 14, 2011 Held-to-Maturity Investment Maturing on July 14, 2011 [Member]	Jun. 30, 2011 Held-to-Maturity Investment Maturing on July 14, 2011 [Member]	Oct. 15, 2010 Held-to-Maturity Investment Maturing on April 15, 2011 [Member]	Dec. 31, 2010 Held-to-Maturity Investment Maturing on April 15, 2011 [Member]	Aug. 10, 2010 Held-to-Maturity Investment Maturing on January 14, 2011 [Member]	Dec. 31, 2010 Held-to-Maturity Investment Maturing on January 14, 2011 [Member]
Payments to acquire time deposit	$ 40,000	$ 0	$ 20,000		$ 20,000		$ 20,000		$ 20,000
Investments held-to-maturity				$ 20,000		$ 20,000		$ 20,000		$ 20,000
Maturity of time deposit, days			185			181		182		157

This item represents investments in debt securities which are categorized as held-to-maturity and that have scheduled maturities within one year of the balance sheet date or the normal operating cycle, whichever is longer; such investments are measured at amortized cost (carrying value). The held-to-maturity category is for those securities that the Entity has the positive intent and ability to hold until maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 3
-Section A
-Paragraph 4, 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 17

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 7, 8, 9, 10, 11

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Description of the maturities of time deposits (including certificates of deposits, individual retirement accounts and open accounts) held by the entity, which may include methodology, assumptions, maturity dates, and other significant factors.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-DEP
-Chapter 13
-Paragraph 42
-Subparagraph a
-IssueDate 2006-05-01

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 15, 17

+ Details

Name:	us-gaap_PaymentsToAcquireInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration