Derivative Financial Instruments Effect of Net Investment Hedge Nonderivative Financial Instrument on OCI (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Gain (loss) recognized in OCI on derivative, (Effective Portion) [Abstract]
Before tax	$ (14,278)	$ 25,760	$ (3,866)
After tax	$ (8,866)	$ 15,825	$ (2,364)

Net Unrealized Gain (Loss) On Nonderivative Net Investment Hedging Instrument Before Tax

No definition available.

Name:	itri_NetUnrealizedGainLossOnNonderivativeNetInvestmentHedgingInstrumentBeforeTax
Namespace Prefix:	itri_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration