Significant Acquisitions and Other Transactions - Dispositions (Details) (Global Tower LLC [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
Sep. 30, 2011	Feb. 11, 2011
Global Tower LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business, productive assets	$ 25.8
Lease agreement, lease back period (in years)	10 years
Capital Lease Obligations		$ 25.8

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant