v2.3.0.15

Fair Value Measurements (Narrative) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2010 | Mar. 31, 2011 Auction Rate Securities, Sold [Member] | Mar. 31, 2011 Auction Rate Securities, Repurchased [Member]
--- | --- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Percent amount of par value at sale |  | 90.00% |
Auction rate securities par value | $ 50.1 | $ 8.1 | $ 42.0

X
- Definition Other Marketable Securities Non-current Auction Rate Securities Par Value + Details
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Namespace Prefix: | esv
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Balance Type: | debit
Period Type: | instant

X
- Definition Percent amount of par value at sale + Details
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Namespace Prefix: | esv
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + Details
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Namespace Prefix: | us-gaap
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration