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Summary of Significant Accounting Policies , Cash, Cash Equivalents and Available-for-sale Investments (Details)
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12 Months Ended |
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Dec. 31, 2013
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| Accounting Policies [Abstract] | |
| Short-term investments, minimum original maturity | 3 months |
| Short-term investments, maximum original maturity | 1 year |
| Long-term investments, minimum original maturity | 1 year |