Stockholders' Equity, Stock Reserved for Future Issuance (Details)	Dec. 31, 2013	Dec. 31, 2012
Common stock options:
Issued and outstanding	6,362,000	6,716,000
Available for future grant	1,286,000
Available for issuance under the Employee Stock Purchase Plan	1,589,000
Issued and outstanding Restricted Stock Units	3,479,000
Senior Convertible Note warrants	19,106,000
Total shares reserved for future issuance	44,241,000
2.75% Senior Convertible Notes due 2017 [Member]
Common stock options:
Senior Convertible Notes	12,419,000