The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Name:	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Summary of Significant Accounting Policies - Additional Information (Details)		9 Months Ended
	Jun. 01, 2014 USD ($)	Sep. 30, 2018 USD ($) Subsidary	Sep. 30, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Marketable Securities, Realized Gain (Loss)		$ 0	$ 0
Impairments of long-lived assets		$ 0	$ 0
Number of subsidiary corporations owned \| Subsidary		7
Maximum
Summary Of Significant Accounting Policies [Line Items]
Marketable securities stated maturity period		1 year
Maximum \| CPRIT
Summary Of Significant Accounting Policies [Line Items]
Research grant contract amount	$ 19,800,000