Investments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2015
Schedule of Investments [Line Items]
Revenue relating to disposal of business		$ 24,388
Minimum [Member] \| Interest-bearing Deposits [Member]
Schedule of Investments [Line Items]
Interest-bearing deposits maturity period	3 months
Maximum [Member] \| Interest-bearing Deposits [Member]
Schedule of Investments [Line Items]
Interest-bearing deposits maturity period	1 year

Amount of gain (loss) on sale or disposal of equity in securities of subsidiaries.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (13)(g)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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- Definition

Period of time between issuance and maturity of customer deposits, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Industry Guide
-Number 3
-Section V
-Paragraph D-E

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+ References

No definition available.

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