Institutional banking has been a money pit more than a profit centre for Commonwealth Bank lately, with an investment program driving costs higher.While the loan impairment expense is most often the swing factor in the performance of this division, discretionary cost increases of 11 per cent, or A$111 million, exceed the rise in loan losses in institutional banking over the last year.CBA chief financial officer David Craig told an investor briefing that this investment program has passed its peak.The rise in loan losses (in keeping with sector trends) was $85 million (up 50 per cent on the year before), with "a small number of large individual provisions" - code for loans to resource company borrowers and select dairy farmers, accounting for most of this.As a result the cash profit for CBA's institutional bank fell nine per cent over 2016 to $1.16 billion.The cost-to-income ratio in this division reached 37.9 per cent in the June half - up from 34.6 per cent in the first half of the year.