Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

Stockholders' Equity [Abstract]

Stock Option Activity

The following table summarizes the stock option activity for the year ended December 31, 2016 (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, 2015		8,041		$	33.21
Granted		2,428		$	54.79
Exercised		(994	)	$	12.63
Cancelled/forfeited/expired		(297	)	$	53.65
Outstanding at December 31, 2016		9,178		$	40.48		4.46		$	122,738
Exercisable at December 31, 2016		4,898		$	28.73		3.40		$	107,969

Restricted Stock Unit Activity

The following table summarizes the RSU activity for the year ended December 31, 2016 (in thousands, except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Non-vested at December 31, 2015		751		$	47.47
Granted		346		$	41.79
Vested		(270	)	$	39.22
Cancelled/forfeited		(49	)	$	49.38
Non-vested at December 31, 2016		778		$	47.68

Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the years ended December 31, 2016, 2015 and 2014 (in thousands), which was allocated as follows and includes $10.1 million and $6.5 million of stock-based compensation expense for Akcea employees in 2016 and 2015, respectively:

	Year Ended December 31,
	2016			2015			2014
Research, development and patents		$	55,099		$	43,638		$	25,843
General and administrative			17,009			15,676			5,540
Total		$	72,108		$	59,314		$	31,383

Weighted-Average Assumptions - ESPP

ESPP:

	December 31,
	2016	2015	2014
Risk-free interest rate	0.4 %	0.1 %	0.1 %
Dividend yield	0.0 %	0.0 %	0.0 %
Volatility	86.4 %	51.7 %	60.1 %
Expected life	6 months	6 months	6 months

Employee Stock Options [Member]

Stockholders' Equity [Abstract]

Weighted-Average Assumptions

For the years ended December 31, 2016, 2015 and 2014, we used the following weighted-average assumptions in our Black-Scholes calculations:

Employee Stock Options:

	December 31,
	2016	2015	2014
Risk-free interest rate	1.5 %	1.5 %	1.7 %
Dividend yield	0.0 %	0.0 %	0.0 %
Volatility	58.7 %	53.8 %	50.1 %
Expected life	4.5 years	4.5 years	4.7 years

Board of Director Stock Options [Member]

Stockholders' Equity [Abstract]

Weighted-Average Assumptions

Board of Director Stock Options:

	December 31,
	2016	2015	2014
Risk-free interest rate	1.3 %	2.1 %	2.2 %
Dividend yield	0.0 %	0.0 %	0.0 %
Volatility	53.1 %	52.2 %	54.2 %
Expected life	6.5 years	6.9 years	6.9 years