Equity Compensation Plans - Stock Incentive Plan (Details Textual) - Stock Incentive Plan 2005	12 Months Ended
	Dec. 31, 2014 shares	Dec. 31, 2015 shares	Dec. 31, 2013 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance under incentive plane	18,700,000		15,800,000
Number of shares counted for every share granted	2
Number of increased authorized shares under incentive plan	2,900,000
Stockholder approved shares available for issuance		4,200,000
Stockholder approved shares available for grant		3,600,000