INVESTMENT SECURITIES - Roll-Forward of Credit Losses on Debt Securities Held by Corporation (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Beginning balance of credit losses on debt securities held for which a portion of an OTTI was recognized in OCI	$ 22,294
Additions:
Credit losses on debt securities for which an OTTI was previously recognized	6,687
Reductions:
Ending balance of credit losses on debt securities held for which a portion of an OTTI was recognized in OCI	28,981
Mortgage Backed Securities Issued By Private Enterprises [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Beginning balance of credit losses on debt securities held for which a portion of an OTTI was recognized in OCI	6,405	$ 5,777
Additions:
Credit losses on debt securities for which an OTTI was previously recognized	387	156
Reductions:
Ending balance of credit losses on debt securities held for which a portion of an OTTI was recognized in OCI	6,792	$ 5,933
US States And Political Subdivisions Member [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Beginning balance of credit losses on debt securities held for which a portion of an OTTI was recognized in OCI	15,889
Additions:
Credit losses on debt securities for which an OTTI was previously recognized	6,300
Reductions:
Ending balance of credit losses on debt securities held for which a portion of an OTTI was recognized in OCI	$ 22,189