Borrowings (Details 4) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Borrowing capacity of CapitalSource Bank with FHLB SF based on pledged collateral
FHLB SF borrowings	$ 480,000	$ 412,000
Unused borrowing capacity	482,218	473,242
FHLB SF Borrowings and FRB Credit Program [Member]
Borrowing capacity of CapitalSource Bank with FHLB SF based on pledged collateral
Borrowing capacity	962,818	885,842
FHLB SF borrowings	(480,000)	(412,000)
Less: outstanding letters of credit	$ (600)	$ (600)