Preferred Stock and Stockholders' Equity (Tables)
 12 Months Ended
Dec. 31, 2015
Preferred Stock and Stockholders' Equity [Abstract]  
Shares of Common Stock Reserved for Future Issuance

 

 

 

 

 

 

Common stock:

 

(in thousands)

Exercise of outstanding options

 

 16,195 

Shares available for grant under stock option plans

 

 8,070 

 

 

 24,265 

 

Summary of Stock Plan Activity

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Outstanding Options

 

 

Shares
Available For
Future Grant 

 

Options
Shares
Subject to
Options
Outstanding

 

Weighted-
Average
Exercise
Price 

 

Weighted-
Average
Remaining
Contractual
Life

 

Aggregate
Intrinsic
Value

 

 

(in thousands)

 

(in thousands)

 

 

 

 

(in years)

 

(in thousands)

Balance at December 31, 2012

 

 4,055 

 

 11,626 

 

$

 2.90 

 

 

 

 

 

Increase in shares authorized for grant

 

 3,992 

 

 —

 

 

 —

 

 

 

 

 

Shares granted

 

 (3,565)

 

 3,565 

 

$

 1.98 

 

 

 

 

 

Shares exercised

 

 —

 

 (35)

 

$

 1.58 

 

 

 

 

 

Shares cancelled and forfeited

 

 444 

 

 (444)

 

$

 4.58 

 

 

 

 

 

Balance at December 31, 2013

 

 4,926 

 

 14,712 

 

$

 2.63 

 

 

 

 

 

Increase in shares authorized for grant

 

 3,993 

 

 —

 

 

 —

 

 

 

 

 

Shares granted

 

 (2,140)

 

 2,140 

 

$

 2.62 

 

 

 

 

 

Shares exercised

 

 —

 

 (1,381)

 

$

 1.34 

 

 

 

 

 

Shares cancelled and forfeited

 

 767 

 

 (767)

 

$

 5.03 

 

 

 

 

 

Balance at December 31, 2014

 

 7,546 

 

 14,704 

 

$

 2.62 

 

 

 

 

 

Increase in shares authorized for grant

 

 4,056 

 

 —

 

 

 

 

 

 

 

 

Shares granted

 

 (4,902)

 

 4,902 

 

$

 3.88 

 

 

 

 

 

Shares exercised

 

 —

 

 (2,041)

 

$

 2.55 

 

 

 

 

 

Shares cancelled and forfeited

 

 1,370 

 

 (1,370)

 

$

 3.07 

 

 

 

 

 

Balance at December 31, 2015

 

 8,070 

 

 16,195 

 

$

 2.98 

 

 6.35 

 

$

 33,318 

 

 

 

 

 

 

 

 

 

 

 

 

 

Options exercisable at December 31, 2015

 

 

 

 10,639 

 

$

 2.71 

 

 5.03 

 

$

 24,250 

 

 

 

 

 

 

 

 

 

 

 

 

 

Options fully vested and expected to vest
at December 31, 2015

 

 

 

 16,195 

 

$

 2.98 

 

 6.35 

 

$

 33,318 

 

Summary of Options Outstanding and Exercisable

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Options Outstanding

 

Options Exercisable

Exercise
Prices of
Options

 

Number of
Shares

 

Weighted-
Average
Remaining
Contractual Life

Weighted-
Average
Exercise
Price

 

Aggregate
Intrinsic
Value

 

Number of
Shares

 

Weighted-
Average
Exercise
Price

 

Aggregate
Intrinsic
Value

 

 

 

 

 

 

(in thousands)

 

(in years)

 

 

 

 

(in thousands)

 

(in thousands)

 

 

 

 

(in thousands)

$

 0.96 

-

$

 2.00 

 

 3,852 

 

3.8

 

$

 1.45 

 

$

 13,564 

 

 3,516 

 

$

 1.43 

 

$

 12,482 

$

 2.01 

-

$

 3.00 

 

 3,813 

 

6.4

 

$

 2.35 

 

 

 10,037 

 

 2,952 

 

$

 2.34 

 

 

 7,784 

$

 3.01 

-

$

 4.00 

 

 4,634 

 

8.6

 

$

 3.32 

 

 

 7,677 

 

 1,415 

 

$

 3.37 

 

 

 2,275 

$

 4.01 

-

$

 6.55 

 

 3,896 

 

6.2

 

$

 4.68 

 

 

 2,040 

 

 2,756 

 

$

 4.42 

 

 

 1,709 

 

 

 

 

 

 

 16,195 

 

6.4

 

$

 2.98 

 

$

 33,318 

 

 10,639 

 

$

 2.71 

 

$

 24,250 

 

Summary of Weighted-Average Assumptions and Resultant Fair Value-Based Measurements for Options Granted to Employees and Directors

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Year Ended December 31,

 

2015

 

2014

 

2013

Weighted-average assumptions for stock options granted:

 

 

 

 

 

 

 

 

Risk-free interest rate

1.77%

 

1.80%

 

1.76%

Expected term

 7.2 

years

 

 6.0 

years

 

 8.3 

years

Expected volatility of stock price

77.0%

 

79.0%

 

83.9%

Dividend rate

0%

 

0%

 

0%

Weighted-average grant date fair value-based measurement

$

2.72

 

$

1.77

 

$

1.54

 

Summary of Stock-Based Compensation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Year ended December 31, 

 

 

2015

 

2014

 

2013

 

 

(in thousands)

Research and development expense

 

$

 839 

 

$

 723 

 

$

 618 

Selling, general and administrative expense

 

 

 5,174 

 

 

 4,478 

 

 

 4,578 

Total

 

$

 6,013 

 

$

 5,201 

 

$

 5,196