Grant Activity (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2015 shares
Restricted Stock Units (RSUs)
Share-based Compensation
Granted (in shares)	2,412
2006 Equity Incentive Plan
Share-based Compensation
Granted (in shares)	1,992
2006 Equity Incentive Plan | Restricted Stock Units (RSUs)
Share-based Compensation
Granted (in shares)	1,355
2006 Equity Incentive Plan | Performance shares
Share-based Compensation
Granted (in shares)	637
2015 Inducement Plan [Member]
Share-based Compensation
Granted (in shares)	178
2015 Inducement Plan [Member] | Restricted Stock Units (RSUs)
Share-based Compensation
Granted (in shares)	70
2015 Inducement Plan [Member] | Performance shares
Share-based Compensation
Granted (in shares)	108
2015 Equity Incentive Plan [Member]
Share-based Compensation
Granted (in shares)	155
2015 Equity Incentive Plan [Member] | Restricted Stock Units (RSUs)
Share-based Compensation
Granted (in shares)	155
Inducement Plan
Share-based Compensation
Granted (in shares)	87
Inducement Plan | Restricted Stock Units (RSUs)
Share-based Compensation
Granted (in shares)	44
Inducement Plan | Performance shares
Share-based Compensation
Granted (in shares)	43