FAIR VALUE (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Financial Assets Measured at Fair Value on Recurring Basis

The following table summarizes our fair value measurements at December 31, 2018 and 2017, 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)
December 31, 2018
Cash equivalents	$	2,024	$	2,024	$	—	$	—
Debt securities:
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations	417		—		417		—
Mortgage-backed securities	2,544		—		2,544		—
Tax-exempt municipal securities	2,771		—		2,771		—
Mortgage-backed securities:
Residential	55		—		55		—
Commercial	523		—		523		—
Asset-backed securities	985		—		985		—
Corporate debt securities	3,142		—		3,142		—
Total debt securities	10,437		—		10,437		—
Total invested assets	$	12,461	$	2,024	$	10,437	$	—
December 31, 2017
Cash equivalents	$	4,564	$	4,564	$	—	$	—
Debt securities:
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations	531		—		531		—
Mortgage-backed securities	1,610		—		1,610		—
Tax-exempt municipal securities	3,889		—		3,889		—
Mortgage-backed securities:
Residential	26		—		26		—
Commercial	456		—		456		—
Asset-backed securities	408		—		408		—
Corporate debt securities	5,382		—		5,381		1
Total debt securities	12,302		—		12,301		1
Total invested assets	$	16,866	$	4,564	$	12,301	$	1