Investments (Details) (Certificates of Deposit)	3 Months Ended
Mar. 31, 2015
Minimum
Schedule of Held-to-maturity Securities [Line Items]
Investment Term	3 months
Maximum
Schedule of Held-to-maturity Securities [Line Items]
Investment Term	18 months

Period of investment, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.