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Significant Accounting Policies, Noncontrolling Interest in Akcea (Details) - Akcea [Member] - shares shares in Millions | 3 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2019 | Dec. 31, 2018 | Apr. 30, 2018 | Jul. 31, 2017 | Jun. 30, 2017
Noncontrolling Interest in Akcea Therapeutics, Inc. [Abstract] |  |  |  |  |
Percentage ownership | 76.00% | 75.00% | 68.00% | 68.00% | 100.00%
Additional shares of Akcea stock received (in shares) | 2.8 |  |  |  |

X
- Definition The number of shares received from the subsidiary during the period. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
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Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |