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Summary of Significant Accounting Policies Cash and Cash Equivalents (Policies)
12 Months Ended
Dec. 31, 2011
Accounting Policies [Abstract]  
Cash and Cash Equivalents
Cash and Cash Equivalents
Cash equivalents are highly liquid investments, which include certificates of deposit, government securities, commercial paper and time deposits with original maturities of three months or less at the time of purchase and are stated at estimated fair value, which approximates cost. Cash is maintained at multiple high-credit quality financial institutions.