Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Stockholders' Equity [Abstract]

Stock Option Activity

The following table summarizes the stock option activity under our stock plans for the year ended December 31, 2018 (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, 2017		9,397		$	44.52
Granted		3,518		$	48.40
Exercised		(1,064	)	$	17.78
Cancelled/forfeited/expired		(540	)	$	52.47
Outstanding at December 31, 2018		11,311		$	47.85		4.41	$	93,663
Exercisable at December 31, 2018		6,071		$	46.83		3.22	$	63,756

RSU Activity

The following table summarizes the RSU activity for the year ended December 31, 2018 (in thousands, except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Non-vested at December 31, 2017		863		$	49.55
Granted		789		$	51.06
Vested		(324	)	$	50.21
Cancelled/forfeited		(82	)	$	51.59
Non-vested at December 31, 2018		1,246		$	50.20

Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the years ended December 31, 2018, 2017 and 2016 (in thousands), which was allocated as follows and includes $44.3 million, $17.5 million and $10.1 million of stock-based compensation expense for Akcea employees in 2018, 2017 and 2016, respectively:

	Year Ended December 31,
	2018		2017		2016
Cost of products sold	$	160	$	—	$	—
Research, development and patent		76,557		64,521		55,099
Selling, general and administrative		54,595		21,454		17,009
Total	$	131,312	$	85,975	$	72,108

Stockholders' Equity [Abstract]

Weighted-Average Assumptions for Stock Options

For the years ended December 31, 2018, 2017 and 2016, we used the following weighted-average assumptions in our Black-Scholes calculations:

Employee Stock Options:

	December 31,
	2018			2017			2016
Risk-free interest rate		2.4	%		1.8	%		1.5	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		63.0	%		65.9	%		58.7	%
Expected life	4.6 years			4.5 years			4.5 years

Board of Director Stock Options:

	December 31,
	2018			2017			2016
Risk-free interest rate		2.8	%		2.2	%		1.3	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		61.5	%		61.2	%		53.1	%
Expected life	6.6 years			6.6 years			6.5 years

Weighted-Average Assumptions for ESPP

ESPP:

	December 31,
	2018			2017			2016
Risk-free interest rate		1.8	%		0.8	%		0.4	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		47.3	%		59.9	%		86.4	%
Expected life	6 months			6 months			6 months

Akcea [Member]

Stockholders' Equity [Abstract]

Weighted-Average Assumptions for Stock Options

In addition to our stock plans, Akcea has its own stock plan under which it grants options and RSUs and under which it derives its stock-based compensation expense. The following are the weighted-average Black-Scholes assumptions Akcea used under its plan for the years ended December 31, 2018, 2017 and 2016:

Employee Stock Options:

	December 31,
	2018			2017			2016
Risk-free interest rate		2.8	%		1.9	%		1.6	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		77.1	%		79.5	%		71.4	%
Expected life	6.08 years			6.06 years			6.08 years

Board of Director Stock Options:

	December 31,
	2018			2017			2016
Risk-free interest rate		2.9	%		1.9	%		2.0	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		78.2	%		79.4	%		79.6	%
Expected life	6.42 years			6.25 years			6.08 years