Stockholders' Equity (Schedule of Warrants) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Warrants
Balance of warrants outstanding at the beginning of the period (in shares)	5,533,242	6,265,620	6,233,483
Granted (in shares)	30,992	30,992	85,470
Exercised (in shares)	(8,333)	(732,378)	(36,666)
Expired (in shares)		(50,000)	(16,667)
Balance of warrants outstanding at the end of the period (in shares)	5,505,901	5,533,242	6,265,620	6,233,483
Weighted-Average Exercise Price Per Share
Weighted average exercise price of warrants at the beginning of the period (in dollars per share)	$ 3.86	$ 3.85	$ 3.87
Granted (in dollars per share)	4.84	4.84	3.51
Exercised (in dollars per share)	3.00	3.77	3.00
Expired (in dollars per share)		8.00	10.80
Weighted average exercise price of warrants at the end of the period (in dollars per share)	$ 3.83	$ 3.86	$ 3.85	$ 3.87
Weighted-Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term	1 year 7 months 6 days	2 years 6 months 11 days	3 years 6 months 26 days	4 years 5 months 23 days