Derivative Financial Instruments Effect of Net Investment Hedge Nonderivative Financial Instrument on OCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Gain (loss) recognized in OCI on derivative, (Effective Portion) [Abstract]
Before tax	$ 0	$ 645	$ 0	$ (14,278)
Net of tax	$ 0	$ 408	$ 0	$ (8,854)

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