Zions Bancorp. in Salt Lake City leaned on its investment portfolio to produce a double-digit increase in profits in the first quarter as it dealt with sluggish commercial loan growth and a big problem loan.

The $64 billion-asset bank reported net earnings of $129 million, up 63% year over year. Earnings per share were 61 cents, well ahead of analysts' average estimate of 54 cents as compiled by FactSet Research Systems.

Net loans and leases rose 3% to $42.7 billion. Consumer loans increased 12% to $9.9 billion, but commercial loans excluding commercial real estate fell 1% to $21.6 billion.

CEO Harris Simmons said in a news release Monday about the quarterly results that "lackluster loan growth" is "a condition which has recently been prevalent throughout the industry."

Net interest income increased 8% to $489 million, driven by a $19 million increase in interest from investment securities. The net interest margin ticked up 3 basis points from the first quarter last year, to 3.38%.

Zions continued to feel the aftereffects of the energy crisis. Credit quality generally improved as net chargeoffs fell by nearly 30% to $46 million, but $14 million of that total came from the oil and gas portfolio, the release said. Zions' oil and gas book shrank 15% year over year to $3.9 billion.

Nearly two-thirds of its chargeoffs were tied to a nonenergy borrower "who is subject to a government investigation and seizure of assets," the release said, though it did not name the borrower.

Zions remains "committed to ... expense control" to improve profits as it shakes off lackluster commercial lending, credit quality and other matters, CEO Harris Simmons says. Bloomberg News

The company cut its provision for credit losses in half to $18 million, but it rose from below $1 million in the fourth quarter mainly because of the big chargeoff to the one borrower, the release said.

Noninterest income increased 13% to $132 million, boosted largely by $8 million of increases each in net securities gains and dividends and other investment income.

Noninterest expenses increased 4.5% to $414 million in the first quarter. Zions said this was driven mainly by $21 million increases in employee salaries and benefits and offset by an $8 million decline in the provision for unfunded lending commitments.

Chairman and CEO Harris H. Simmons summed up the quarter by saying credit quality was "generally strong and improving," but he acknowledged the big problem loan and other challenges to be dealt with.

“While operating costs were seasonally higher, we remain committed to a continued focus on expense control and improvement in our profitability through the remainder of 2017 and beyond,” Simmons said in the release.