Significant Accounting Policies, Noncontrolling Interest in Akcea (Details) - Akcea [Member] - shares shares in Millions	1 Months Ended	7 Months Ended
	Oct. 31, 2018	Jul. 31, 2017	Sep. 30, 2018	Apr. 30, 2018	Mar. 31, 2018
Noncontrolling Interest in Akcea Therapeutics, Inc. [Abstract]
Percentage ownership before IPO		100.00%
Percentage ownership		68.00%	75.00%	75.00%	68.00%
Subsequent Event [Member]
Noncontrolling Interest in Akcea Therapeutics, Inc. [Abstract]
Percentage ownership	76.00%
Additional shares of Akcea stock received when TEGSEDI received marketing authorization in the U.S. (in shares)	1.7