HELD-TO-MATURITY SECURITIES - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Held-to-maturity Securities [Abstract]
Available For Sale Securities Transferred To Held To Maturity Securities		$ 3,000,000,000
Unrealized Net Losses Recognized In Oci At Time Of Transfer Of Available For Sale Securities Transferred To Held To Maturity Securities		$ 6,000,000
Other than temporary impairment losses, held-to-maturity securities	$ 0

The amount by which the fair value of an investment in debt securities categorized as Held-to-maturity is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Name:	us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsHeldtomaturitySecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration