.5 million respectively , in restricted cash . at december 31 , 2006 and 2005 the balance was held in deposit with certain banks predominantly to collateralize conditional stand-by letters of credit in the names of the company 2019s landlords pursuant to certain operating lease agreements . h . property and equipment property and equipment consist of the following at december 31 ( in thousands ) : depreciation and amortization expense for the years ended december 31 , 2006 , 2005 and 2004 was $ 25