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Fair Value Measurement (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Auction rate security bond par value $ 1,000,000 $ 1,000,000
Percentage of auction rate security guaranteed 97.00% 97.00%
Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Percentage of carrying value of auction rate securities 1.00% 1.00%
Maximum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Percentage of carrying value of auction rate securities 4.00% 4.00%