Hi Aji,
As per my understanding you have maintained OMRW settings with following parameter's.
Company code | ERD Settings as Blank | Exchange rate type as Blank | Currency type as 10|
If yes , Exchange rate will post ,rate difference between GR and IR. I mean while posting the GR > your IDR X USD rate is 100.00 ,but while posting the IR > Your exchange rate is 102.00. 2 IDR will post in Different exchange rate GL accounts & moreover GL accounts picking from KDF in OBA1.
Mentioned link can help to you about exchange rate Diff treatment.
http://help.sap.com/saphelp_470/helpdata/en/a8/b997be452b11d189430000e829fbbd/content.htm
http://help.sap.com/erp2005_ehp_05/helpdata/EN/45/5c4a52eedd2f95e10000000a155369/content.htm
Regards
Mani Kumar