This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Investment in Silver Creek - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Equity method investment	$ 8,893	$ 10,551
Silver Creek Pharmaceuticals Inc [Member]
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Equity method investment	$ 8,900
Silver Creek Pharmaceuticals Inc [Member] \| Maximum [Member]
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Ownership interest percentage held by parent			50.00%