Equity Incentive Plans, Share-based Payment Award (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of unearned share-based compensation expected to be recognized (in years)	2.02
Closing price of company's common stock related to calculation of aggregate intrinsic value of stock options (in dollars per share)	$ 37.20
Restricted stock units' weighted average remaining expense recognition period (in years)	2.02
Amount of unearned share-based compensation estimated to be expensed related to unvested share-based payment awards	$ 69.6
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
RSU nonvested shares beginning balance	5,241,306	4,637,948	3,601,772
RSU shares granted	1,627,000	1,766,257	1,846,241
RSU shares forfeited/expired	(185,000)	(171,967)	(120,198)
RSU shares vested	(1,191,000)	(990,932)	(689,867)
RSU nonvested shares ending balance	5,492,220	5,241,306	4,637,948
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of unearned share-based compensation expected to be recognized (in years)	2.06
Total intrinsic value of RSU's vested during the period	43.7	32.6	17.5
Total intrinsic value of RSU's outstanding	$ 204.3
Restricted stock units' weighted average remaining expense recognition period (in years)	2.06
Weighted average fair values per share of restricted stock units awarded (amount per share)	$ 30.48	26.05	20.75

Closing price per share of company's common stock at balance sheet date

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- Definition

The intrinsic value of share-based payment equity instruments, excluding stock options, outstanding during the reporting period as calculated by applying the disclosed pricing methodology.

+ References

No definition available.

+ Details

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- Definition

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

+ References

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- Definition

The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

+ References

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

-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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

+ References

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