Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands		6 Months Ended
	Dec. 31, 2017	Jun. 30, 2018	Jan. 01, 2018
Summary Of Significant Accounting Policies [Line Items]
Percentage allocation on source of revenue		88.00%
Reclassification from accumulated other comprehensive income to retained earnings	$ 109
Accounting Standards Update 2016-01 [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional income recorded from changes in accounting for equity investments		$ 4
Accounting Standards Update 2016-01 [Member] \| Retained Earnings [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment from accumulated other comprehensive income to retained earnings			$ 29