NEW YORK (CNN/Money) - Travelers Property Casualty Corp., the year's biggest initial public offering, continued the trend of strong insurance IPOs when it closed up nearly 6 percent on the New York Stock Exchange Friday.

Shares of Travelers (TAP.A: Research, Estimates) closed at $19.56 Friday, a $1.06 gain on the insurer's offering price.

Travelers, a unit of Citigroup, raised $3.9 billion late Thursday when it sold 210 million shares at $18.50 each via Salomon Smith Barney. The company had planned to sell 210 million shares at $16 to $19 each.

Travelers, a leading property and casualty insurer in the United States and the third-largest underwriter of commercial lines, initially filed for an IPO on Feb. 8. The offering is also the biggest insurance IPO ever.

Citigroup (C: Research, Alcon (ACL: Research, Estimates) issue rose 3 percent in its market debut Thursday.

At $3.9 billion, Travelers also trounced the record set by Prudential Financial Inc. which in December raised $3 billion, the largest insurance offering at that time. Prudential (PRU: Research, Estimates) gained nearly 7 percent in its market debut last year.