Segment Reporting (Summary Of Segment Performance) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Revenue:
License	$ 232.3	$ 225.0	$ 613.1	$ 644.2
Maintenance	288.7	272.3	853.0	807.4
Professional services	59.2	50.9	166.7	155.7
Total revenue	580.2	548.2	1,632.8	1,607.3
Direct and allocated indirect segment operating expenses:	370.0	335.5	1,076.2	1,007.7
Segment operating income (loss)	210.2	212.7	556.6	599.6
Unallocated operating expenses	(62.6)	(50.9)	(197.0)	(161.7)
Other loss, net	(10.6)	(3.5)	(25.4)	(9.9)
Earnings before income taxes	137.0	158.3	334.2	428.0
Enterprise Service Management [Member]
Revenue:
License	131.3	133.7	357.4	398.2
Maintenance	164.3	147.7	482.8	434.5
Professional services	59.2	50.9	166.7	155.7
Total revenue	354.8	332.3	1,006.9	988.4
Direct and allocated indirect segment operating expenses:	284.2	256.1	832.8	763.8
Segment operating income (loss)	70.6	76.2	174.1	224.6
Enterprise Service Management [Member] \| Solutions [Member]
Revenue:
License	131.3	133.7	357.4	398.2
Maintenance	164.3	147.7	482.8	434.5
Total revenue	295.6	281.4	840.2	832.7
Direct and allocated indirect segment operating expenses:	224.1	199.1	652.3	597.9
Segment operating income (loss)	71.5	82.3	187.9	234.8
Enterprise Service Management [Member] \| Services [Member]
Revenue:
Professional services	59.2	50.9	166.7	155.7
Total revenue	59.2	50.9	166.7	155.7
Direct and allocated indirect segment operating expenses:	60.1	57.0	180.5	165.9
Segment operating income (loss)	(0.9)	(6.1)	(13.8)	(10.2)
Mainframe Service Management [Member]
Revenue:
License	101.0	91.3	255.7	246.0
Maintenance	124.4	124.6	370.2	372.9
Total revenue	225.4	215.9	625.9	618.9
Direct and allocated indirect segment operating expenses:	85.8	79.4	243.4	243.9
Segment operating income (loss)	$ 139.6	$ 136.5	$ 382.5	$ 375.0

Segment operating income loss.

No definition available.

Name:	bmc_SegmentOperatingIncomeLoss
Namespace Prefix:	bmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Direct segment operating expenses includes the allocation of certain indirect expenses that are directly allocated to particular segments and are controllable by segment management.

+ References

No definition available.

+ Details

Name:	bmc_SegmentReportingInformationDirectAndAllocatedIndirectExpenses
Namespace Prefix:	bmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The sum of total unallocated indirect expenses that primarily includes operating expenses not specifically identified to a particular segment or controllable by segment management.

+ References

No definition available.

+ Details

Name:	bmc_SegmentReportingInformationUnallocatedExpenses
Namespace Prefix:	bmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Article 5

+ Details

Name:	us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Revenue earned during the period relating to consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity.

+ References

+ Details

Name:	us-gaap_LicensesRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Revenue derived from maintenance services provided under contracts or arrangements with clients. For example, it may include the maintenance of software, plant and equipment, and facilities.

+ References

+ Details

Name:	us-gaap_MaintenanceRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

+ References

+ Details

Name:	us-gaap_NonoperatingIncomeExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

+ References

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_SegmentReportingInformationRevenueAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue from providing technology services. The services may include training, installation, engineering or consulting. Consulting services often include implementation support, software design or development, or the customization or modification of the licensed software.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(d))

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 605

-Section 25

-Paragraph 76

-URI http://asc.fasb.org/extlink&oid=19772080&loc=d3e132428-111767

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 97-2

-Paragraph 63

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_TechnologyServicesRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration