Investments (Details Textual) (USD $) In Millions, unless otherwise specified	6 Months Ended		3 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Auction rate notes [Member]	Jun. 30, 2014 Minimum [Member]	Jun. 30, 2014 Maximum [Member]	Jun. 30, 2014 Maximum [Member] Auction rate notes [Member]	Jun. 30, 2014 Long Term Investments [Member] Auction rate notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of auction-rate notes sold at par value						$ 2.9
Short-term investments, minimum maturity period	1 month
Short -term investments, maximum maturity period	2 years
Short-term interest rate reset dates of auction rate note securities	less than ninety days
Auction rate note securities with contractual maturities	excess of ten years
Reset period for the securities held	seven or twenty-eight days
Period for Principal Repayments of Securities by Issuer			31 years	33 years
Comprehensive income net of tax due to auction rate notes		0.1
Comprehensive income before tax due to auction rate notes		$ 0.1
Maximum interest rate					one month LIBOR plus 1.5%