Washington Mutual Inc. said it completed its $6.9-billion purchase of H.F. Ahmanson & Co., the Irwindale-based parent company of Home Savings. Washington Mutual, the largest U.S. savings and loan, now has $156.2 billion in assets and has extended its reach to more than 2,000 offices. The Seattle-based thrift entered California two years ago when it bought American Savings. It acquired Golden West Financial Corp. and Ahmanson shortly afterward. Ahmanson shareholders receive 1.68 shares of Washington Mutual common stock for each share of Ahmanson common stock. Washington Mutual shares fell $2.88 to close at $30.88 on Nasdaq; Ahmanson shares fell $3.19 to $52.31 on the NYSE.