Income Taxes (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Feb. 29, 2012 2007 Tax Year [Member] Brazil [Member]
Income Taxes (Textual) [Abstract]
Total tax assessment including interest and penalty	$ 17.0	$ 35.1

Amount of tax assessment including interest and penalties.

No definition available.

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Namespace Prefix:	do_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant