Investments (Tables)

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Maturities for short-term investments

The estimated fair values of short-term investments, which approximate cost at December 31, 2016, are shown below by contractual maturity. Actual maturities may differ from contractual maturities because issuers of the securities may have the right to retire our investments without prepayment penalties.

(in millions)	Available- For-Sale
Due in one year or less	$	160
Due after one year through three years	239
Due after three years through five years	65
Due after five years	23
Total	$	487