SCHEDULE 13G

Amendment No. 1
Bucyrus International Incorporated
Class A Common Stock
Cusip #118759109


Cusip #118759109
Item 1:	Reporting Person - FMR LLC
Item 4:	Delaware
Item 5:	1,027,275
Item 6:	0
Item 7:	1,642,856
Item 8:	0
Item 9:	1,642,856
Item 11:	2.028%
Item 12:	    HC


Cusip #118759109
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	1,642,856
Item 8:	0
Item 9:	1,642,856
Item 11:	2.028%
Item 12:	IN




	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



Item 1(a).	Name of Issuer:

		Bucyrus International Incorporated

Item 1(b).	Name of Issuer's Principal Executive Offices:

		1100 Milwaukee Avenue
		P.O. Box 500
		South Milwaukee, WI  53172


Item 2(a).	Name of Person Filing:

		FMR LLC

Item 2(b).	Address or Principal Business Office or, if None,
Residence:

		82 Devonshire Street, Boston,
Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Class A Common Stock

Item 2(e).	CUSIP Number:

		118759109

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
and the person filing, FMR LLC, is a parent holding company
in accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See
Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	1,642,856

	(b)	Percent of Class:	2.028%

	(c)	Number of shares as to which such
person has:

	(i)	sole power to vote or to direct
the vote:	1,027,275

	(ii)	shared power to vote or to
direct the vote:	0

	(iii)	sole power to dispose or to
direct the disposition of:	1,642,856

	(iv)	shared power to dispose or to
direct the disposition of:	0



Item 5.	Ownership of Five Percent or Less of a Class.

	If this statement is being filed to report the fact that as of the
date hereof, the reporting person has ceased to be the
beneficial owner of more than five percent of the class of
securities, check the following (X).

Item 6.	Ownership of More than Five Percent on Behalf of Another
Person.

	Not applicable

Item 7.	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent
Holding Company.

	See attached Exhibit A.

Item 8.	Identification and Classification of Members of
the Group.

	Not applicable.  See attached Exhibit A.

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certifications.

	Inasmuch as the reporting persons are no longer the beneficial
owners of more than five percent of the number of shares
outstanding, the reporting persons have no further reporting
obligation under Section 13(d) of the Securities and Exchange
Commission thereunder, and the reporting persons have no
obligation to amend this Statement if any material change
occurs in the facts set forth herein.  I also certify that, to the
best of my knowledge and belief, FIL Limited and its various
non-U.S. investment management subsidiaries included on
this Schedule 13G are subject to a regulatory scheme
substantially comparable to the regulatory scheme applicable
to the functionally equivalent U.S. institutions.  I also
undertake to furnish to the Commission staff, upon request,
information that would otherwise be disclosed in a Schedule
13D with respect to FIL Limited and its various non-U.S.
investment management subsidiaries included on this
Schedule 13G.

Signature

	After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement
is true, complete and correct.

December 09, 2010
Date

 /s/ Scott C. Goebel
Signature

Scott C. Goebel
Duly authorized under Power of Attorney
effective as of June 1, 2008 by and on behalf of FMR LLC
and its direct and indirect  subsidiaries


	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



	Pursuant to the instructions in Item 7 of Schedule 13G,
Fidelity Management & Research Company ("Fidelity"), 82
Devonshire Street, Boston, Massachusetts 02109, a wholly-
owned subsidiary of FMR LLC and an investment adviser
registered under Section 203 of the Investment Advisers Act
of 1940, is the beneficial owner of 435,300 shares or 0.537%
of the Class A Common Stock outstanding of Bucyrus
International Incorporated  ("the Company") as a result of
acting as investment adviser to various investment companies
registered under Section 8 of the Investment Company Act of
1940.

	Edward C. Johnson 3d and FMR LLC, through its
control of Fidelity, and the funds each has sole power to
dispose of the 435,300 shares owned by the Funds.

	Members of the family of Edward C. Johnson 3d,
Chairman of FMR LLC, are the predominant owners, directly
or through trusts, of Series B voting common shares of FMR
LLC, representing 49% of the voting power of FMR LLC.
The Johnson family group and all other Series B shareholders
have entered into a shareholders' voting agreement under
which all Series B voting common shares will be voted in
accordance with the majority vote of Series B voting common
shares.  Accordingly, through their ownership of voting
common shares and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed,
under the Investment Company Act of 1940, to form a
controlling group with respect to FMR LLC.

	Neither FMR LLC nor Edward C. Johnson 3d,
Chairman of FMR LLC, has the sole power to vote or direct
the voting of the shares owned directly by the Fidelity Funds,
which power resides with the Funds' Boards of Trustees.
Fidelity carries out the voting of the shares under written
guidelines established by the Funds' Boards of Trustees.

	Strategic Advisers, Inc., 82 Devonshire Street, Boston,
MA 02109, a wholly-owned subsidiary of FMR LLC and an
investment adviser registered under Section 203 of the
Investment Advisers Act of 1940, provides investment
advisory services to individuals.  As such, FMR LLC's
beneficial ownership includes 515 shares, or 0.001%, of the
Class A Common Stock outstanding of Bucyrus International
Incorporated, beneficially owned through Strategic Advisers,
Inc.

	Pyramis Global Advisors, LLC ("PGALLC"), 900
Salem Street, Smithfield, Rhode Island, 02917, an indirect
wholly-owned subsidiary of FMR LLC and an investment
adviser registered under Section 203 of the Investment
Advisers Act of 1940, is the beneficial owner of 165,770
shares or 0.205% of the outstanding Class A Common Stock
of Bucyrus International Incorporated as a result of its serving
as investment adviser to institutional accounts, non-U.S.
mutual funds, or investment companies registered under
Section 8 of the Investment Company Act of 1940 owning
such shares.

	Edward C. Johnson 3d and FMR LLC, through its
control of PGALLC, each has sole dispositive power over
165,770 shares and sole power to vote or to direct the voting
of 165,770 shares of Class A Common Stock owned by the
institutional accounts or funds advised by PGALLC as
reported above.

	Pyramis Global Advisors Trust Company ("PGATC"),
900 Salem Street, Smithfield, Rhode Island, 02917, an indirect
wholly-owned subsidiary of FMR LLC and a bank as defined
in Section 3(a)(6) of the Securities Exchange Act of 1934, is
the beneficial owner of 744,111 shares or 0.919% of the
outstanding Class A Common Stock of the Bucyrus
International Incorporated as a result of its serving as
investment manager of institutional accounts owning such
shares.

	Edward C. Johnson 3d and FMR LLC, through its
control of Pyramis Global Advisors Trust Company, each has
sole dispositive power over 744,111 shares and sole power to
vote or to direct the voting of 570,090 shares of Class A
Common Stock owned by the institutional accounts managed
by PGATC as reported above.

	FIL Limited ("FIL"), Pembroke Hall, 42 Crow Lane,
Hamilton, Bermuda, and various foreign-based subsidiaries
provide investment advisory and management services to a
number of non-U.S. investment companies and certain
institutional investors.  FIL, which is a qualified institution
under section 240.13d-1(b)(1)(ii), is the beneficial owner of
297,160 shares or 0.367% of the Class A Common Stock
outstanding of the Company.

	Partnerships controlled predominantly by members of
the family of Edward C. Johnson 3d, Chairman of FMR LLC
and FIL, or trusts for their benefit, own shares of FIL voting
stock with the right to cast approximately 47% of the total
votes which may be cast by all holders of FIL voting stock.
FMR LLC and FIL are separate and independent corporate
entities, and their Boards of Directors are generally composed
of different individuals.

	FMR LLC and FIL are of the view that they are not
acting as a "group" for purposes of Section 13(d) under the
Securities Exchange Act of 1934 (the "1934" Act) and that
they are not otherwise required to attribute to each other the
"beneficial ownership" of securities "beneficially owned" by
the other corporation within the meaning of Rule 13d-3
promulgated under the 1934 Act.  Therefore, they are of the
view that the shares held by the other corporation need not be
aggregated for purposes of Section 13(d). However, FMR
LLC is making this filing on a voluntary basis as if all of the
shares are beneficially owned by FMR LLC and FIL on a joint
basis.

	FIL has sole dispositive power over 297,160 shares
owned by the International Funds. FIL has sole power to vote
or direct the voting of 290,900 shares and no power to vote or
direct the voting of 6,260 shares of Class A Common Stock
held by the International Funds as reported above.


	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
	RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on December 09, 2010, agree
and consent to the joint filing on their behalf of this Schedule
13G in connection with their beneficial ownership of the Class
A Common Stock of Bucyrus International Incorporated at
November 30, 2010.

	FMR LLC

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Duly authorized under Power of Attorney effective as
of June 1, 2008, by and on behalf of FMR LLC and its direct
and indirect subsidiaries

	Edward C. Johnson 3d

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Duly authorized under Power of Attorney effective as
of June 1, 2008, by and on behalf of Edward C. Johnson 3d

	Fidelity Management & Research Company

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Senior V.P. and General Counsel