Time Warner Cable reported an 18 percent increase in first-quarter net income Thursday as acquisitions and new broadband customers boosted revenue.

The New York-based company’s stock fell $2.15, or 2.6 percent, to $80 in late morning trading after initially spiking to $83.64, the highest level since the split from parent company Time Warner Inc. was finalized in 2009.

The company said net income was $382 million, or $1.20 per share, in the January-to-March period, up from $325 million, or 93 cents per share, a year earlier.

Time Warner Cable earned $1.30 per share after adjusting for one-time items. That was 7 cents more than the average estimate of analysts surveyed by FactSet.

Overall revenue rose 6 percent to $5.13 billion from $4.83 billion. That was slightly below expectations of $5.14 billion.

Excluding acquisitions, revenue would have risen 3 percent, chiefly because of increasing revenue from broadband. Time Warner Cable has both recruited new broadband subscribers and raised prices for existing ones.

Revenue from cable TV continued to decline, excluding acquisitions, as subscriber cancellations outweighed price increases and a shift toward higher-priced or bigger channel packages.

During the quarter, the company lost 94,000 basic video subscribers. That was offset in part by a net gain of 214,000 broadband accounts and 112,000 voice customers.

Time Warner Cable added a net 592,000 cable TV customers since the end of 2011, mainly through the acquisition of Insight Communications, a cable company with customers in Indiana, Kentucky and Ohio. That deal closed in February.

But cable TV subscriptions have been declining across the industry for years as viewers shift to satellite and phone company TV services.