Exhibit 24

                               POWER OF ATTORNEY
                         For Executing Forms 3, 4 and 5

     Know all by these presents that the undersigned, James J. Cleary, hereby
constitutes and appoints each of Regina Gregory and Amanda B. Warrington,
signing singly, his true and lawful attorney-in-fact to:

     (1)     execute for and on behalf of the undersigned Forms 3, 4 and 5 in
accordance with Section 16(a) of the Securities Exchange Act of 1934 and the
rules thereunder;

     (2)     do and perform any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete the execution of any
such Form 3, 4 or 5 and the timely filing of such form with the United States
Securities and Exchange Commission and any other authority; and

     (3)     take any other action of any type whatsoever in connection with the
foregoing, including the execution of a Form ID (Uniform Application for Access
Codes to File on Edgar,) which, in the opinion of such attorney-in-fact, may be
of benefit to, in the best interest of, or legally required by, the undersigned,
it being understood that the documents executed by such attorney-in-fact on
behalf of the undersigned pursuant to this Power of Attorney shall be in such
form and shall contain such terms and conditions as such attorney-in-fact may
approve, in his or her discretion.

The undersigned hereby grants to such attorney-in-fact full power and authority
to do and perform all and every act and thing whatsoever requisite, necessary
and proper to be done in the exercise of any of the rights and powers herein
granted, as fully to all intents and purposes as such attorney-in-fact might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or his or her
substitute or substitutes, shall lawfully do or cause to be done by virtue of
this power of attorney and the rights and powers herein granted. The undersigned
acknowledges that the foregoing attorney-in-fact, in serving in such capacity at
the request of the undersigned, is not assuming any of the undersigned's
responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 30th day of December, 2013.

By: /s/ James J. Cleary
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Name: James J. Cleary