FAIR VALUE (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

Financial Assets Measured at Fair Value on Recurring Basis

The following table summarizes our fair value measurements at March 31, 2016 and December 31, 2015, respectively, for financial assets measured at fair value on a recurring basis:

	Fair Value Measurements Using
	Fair Value		Quoted Prices in Active Markets (Level 1)		Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
	(in millions)
March 31, 2016
Cash equivalents	$	2,669	$	2,669	$	—	$	—
Debt securities:
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations	453		—		453		—
Mortgage-backed securities	2,034		—		2,034		—
Tax-exempt municipal securities	3,038		—		3,035		3
Mortgage-backed securities:
Residential	11		—		11		—
Commercial	859		—		859		—
Asset-backed securities	253		—		252		1
Corporate debt securities	3,030		—		3,025		5
Total debt securities	9,678		—		9,669		9
Total invested assets	$	12,347	$	2,669	$	9,669	$	9
December 31, 2015
Cash equivalents	$	2,229	$	2,229	$	—	$	—
Debt securities:
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations	332		—		332		—
Mortgage-backed securities	1,891		—		1,891		—
Tax-exempt municipal securities	2,668		—		2,663		5
Mortgage-backed securities:
Residential	13		—		13		—
Commercial	985		—		985		—
Asset-backed securities	263		—		263		—
Corporate debt securities	2,958		—		2,952		6
Total debt securities	9,110		—		9,099		11
Total invested assets	$	11,339	$	2,229	$	9,099	$	11

Changes in Fair Value of Assets Measured Using Significant Unobservable Inputs

During the three months ended March 31, 2016 and 2015, the changes in the fair value of the assets measured using significant unobservable inputs (Level 3) were comprised of the following:

	For the three months ended March 31,
	2016								2015
	Private Placements		Auction Rate Securities			Total			Private Placements			Auction Rate Securities			Total
	(in millions)
Beginning balance at January 1	$	6	$	5		$	11		$	24		$	8		$	32
Total gains or losses:
Realized in earnings	—		—			—			—			—			—
Unrealized in other comprehensive income	—		—			—			—			—			—
Purchases	—		—			—			—			—			—
Sales	—		—			—			(18		)	(2		)	(20		)
Settlements	—		(2		)	(2		)	—			—			—
Balance at March 31	$	6	$	3		$	9		$	6		$	6		$	12