Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Stockholders' Equity [Abstract]

Stock Option Activity

The following table summarizes the stock option activity for the year ended December 31, 2015 (in thousands, except per share and contractual life data):

	Number of Shares			Weighted Average Exercise Price Per Share		Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding at December 31, 2014		7,379		$	19.52
Granted		2,550		$	61.02
Exercised		(1,674	)	$	14.07
Cancelled/forfeited/expired		(214	)	$	42.43
Outstanding at December 31, 2015		8,041		$	33.21		4.57		$	232,581
Exercisable at December 31, 2015		3,940		$	16.43		3.32		$	179,273

Restricted Stock Unit Activity

The following table summarizes the RSU activity for the year ended December 31, 2015 (in thousands, except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Non-vested at December 31, 2014		638		$	30.52
Granted		348		$	65.69
Vested		(196	)	$	27.40
Cancelled/forfeited		(39	)	$	42.87
Non-vested at December 31, 2015		751		$	47.47

Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the years ended December 31, 2015, 2014 and 2013 (in thousands), which was allocated as follows and includes $6.5 million of stock-based compensation expense for Akcea employees in 2015:

	Year Ended December 31,
	2015			2014			2013
Research, development and patents		$	43,638		$	25,843		$	9,673
General and administrative			15,676			5,540			1,745
Total		$	59,314		$	31,383		$	11,418

Weighted-Average Assumptions - ESPP

ESPP:

	December 31,
	2015	2014	2013
Risk-free interest rate	0.1 %	0.1 %	0.1 %
Dividend yield	0.0 %	0.0 %	0.0 %
Volatility	51.7 %	60.1 %	62.9 %
Expected life	6 months	6 months	6 months

Employee Stock Options [Member]

Stockholders' Equity [Abstract]

Weighted-Average Assumptions

For the years ended December 31, 2015, 2014 and 2013, we used the following weighted-average assumptions in our Black-Scholes calculations:

Employee Stock Options:

	December 31,
	2015	2014	2013
Risk-free interest rate	1.5 %	1.7 %	1.1 %
Dividend yield	0.0 %	0.0 %	0.0 %
Volatility	53.8 %	50.1 %	51.1 %
Expected life	4.5 years	4.7 years	5.1 years

Board of Director Stock Options [Member]

Stockholders' Equity [Abstract]

Weighted-Average Assumptions

Board of Director Stock Options:

	December 31,
	2015	2014	2013
Risk-free interest rate	2.1 %	2.2 %	2.2 %
Dividend yield	0.0 %	0.0 %	0.0 %
Volatility	52.2 %	54.2 %	52.7 %
Expected life	6.9 years	6.9 years	7.2 years