Investments (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Certificates of deposits	$ 12,900	$ 11,400
Certificates of deposit interest rate, lower range	0.25%
Certificates of deposit interest rate, upper range	0.90%
Investments held to maturity	$ 19,338	$ 15,987
Minimum [Member]
Schedule of Investments [Line Items]
Certificates of deposit maturity dates	2 months
Investments maturity dates	1 month
Maximum [Member]
Schedule of Investments [Line Items]
Certificates of deposit maturity dates	18 months
Investments maturity dates	18 months