Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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-Section 50
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Recently Issued Authoritative Accounting Guidance - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2018	Jun. 30, 2019	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Federal statutory tax rate		21.00%	35.00%
Accounting Standards Update 2018-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Reclassification of standard tax debit within accumulated other comprehensive income to retained earnings	$ 5,759,000