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LOAN COMMITMENTS AND OTHER RELATED ACTIVITIES - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
	Aug. 22, 2016	Mar. 31, 2018	Mar. 31, 2017
Other Commitments [Line Items]
Commitments to make loans, period, maximum		30 days
Alternative investments unfunded investment commitments		$ 50.1
Affordable Housing Fund Investment
Other Commitments [Line Items]
Alternative investments unfunded investment commitments		15.6
Small Business Investment Companies
Other Commitments [Line Items]
Alternative investments unfunded investment commitments		10.7
Other Investments
Other Commitments [Line Items]
Alternative investments unfunded investment commitments		50.6
Los Angeles Football Club (LAFC) Naming Rights, Revenue Rights, And Other Sponsorship Rights
Other Commitments [Line Items]
Maximum commitment			$ 100.0
Related party term of contract	15 years		15 years
Payments for naming rights		11.3	$ 10.0
Prepaid commitment balance, net of amortization		$ 9.7

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

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