Property and casualty insurer Travelers Cos. said on Tuesday Alan Schnitzer would take over as chief executive from Jay Fishman in December.

Fishman, 62, has led the company since April 2004 when The St. Paul Companies, which he previously led, merged with Travelers Property Casualty Corp. Under his watch, Travelers' stock value has more than doubled.

Fishman has aggressively raised insurance prices in the past several quarters to combat low interest rates that have kept a lid on insurers' investment income over the past few years.

Fishman had said in November that he had been diagnosed with a neuromuscular condition.

Schnitzer, 49, is the chief executive of Travelers' business and international insurance, the company's biggest business and has been with the company since April 2007.

Fishman will become executive chairman after Schnitzer's appointment, Travelers said.

The company's stock was marginally lower at $106.50 in extended trading.