Long-Term Obligations and Commitments, Operating Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Building Option	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Annual Future Minimum Payments Under Operating Leases [Abstract]
2016	$ 1,879
2017	1,878
2018	1,597
2019	1,474
2020	1,527
Thereafter	16,125
Total minimum payments	24,480
Office and Laboratory Space [Member]
Annual Future Minimum Payments Under Operating Leases [Abstract]
Rent expense	2,000	$ 1,800	$ 1,800
Deferred rent	$ 2,000	$ 1,800
Office and Laboratory Space [Member] | Akcea Therapeutics [Member]
Operating Leases [Abstract]
Number of buildings in Carlsbad, California | Building	3
Office and Laboratory Space [Member] | Manufacturing Facility [Member]
Operating Leases [Abstract]
Number of options to extend lease | Option	4
Term of lease extension	5 years
Office and Laboratory Space [Member] | Building [Member]
Operating Leases [Abstract]
Number of options to extend lease | Option	2
Term of lease extension	5 years
Office and Laboratory Space [Member] | Building [Member] | Akcea Therapeutics [Member]
Operating Leases [Abstract]
Term of lease	3 years