CBA's New Zealand unit, ASB, has reported a net profit of NZ$593 million for the six months ending December 31 2017, as its impaired debt charges dropped and its lending expanded.Cash earnings rose to NZ$575 million, up from NZ$502 million a year earlier.The 47 per cent drop in impairment losses (down to NZ$26 million) was largely due to a recovery in dairy prices, and contributed to the 13 per cent increase in net profit compared with the previous corresponding period.Home loans increased by five per cent, and business, commercial and rural lending grew by eight per cent, contributing to a six per cent total increase in customer lending."In addition, customer deposits grew by eight per cent in a competitive market for bank deposits," said an ASB media release. "We are seeing a continued trend around customers focusing on increasing savings and taking advantage of the current low interest rate environment to pay down debt," said new ASB CEO Vittoria Shortt.In contrast to other banks, ASB's full-time equivalent staff numbers rose to 4,826 (up from 4,697 a year earlier) with most of the increase in frontline and compliance staff. That contributed to a 3.4 per cent increase in operating costs in the six months to December last year.