Investments - Short Term Investments (Tables)

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Investments Classified by Contractual Maturity Date

The estimated fair values of short-term investments, which approximate cost at December 31, 2014, are shown below by contractual maturity. Actual maturities may differ from contractual maturities because the issuers of the securities may have the right to retire our investments without prepayment penalties.

(in millions)	Available- For-Sale
December 31, 2014
Due in one year or less	$	175
Due after one year through three years	791
Due after three years through five years	163
Due after five years	88
Total	$	1,217