Please post the DDL, including all indexes, for the "prj_detail" table.
If the clustered index is on an identity column, you should almost certainly change it to "accounting_period" instead. This is especially true if, as is extremely likely, you (almost) always specify an accounting_period / period range in your queries on this table.
SQL DBA,SQL Server MVP('07, '08, '09)
Prosecutor James Blackburn, in closing argument in the "Fatal Vision" murders trial: "If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them."