Common Stock, Employee Stock Purchase Plan (Details) (Employee Stock Purchase Plan [Member], USD $)	12 Months Ended
	Dec. 31, 2014
Employee Stock Purchase Plan [Member]
Employee Stock Purchase Plan Disclosures [Line Items]
Employee payroll deductions, minimum	$ 10
Employee payroll deductions maximum	$ 350
Discount on the fair market value of shares purchased as of the offering date (in hundredths)	5.00%
Maximum number of shares of common stock available to be purchased per participant per offering period (in shares)	62
Maximum number of shares of common stock which may be purchased under the ESPP (in shares)	734,000
Number of shares of common stock available for purchase under the ESPP (in shares)	396,910