The improved package includes more than doubling the council's ''first loss'' cover, from $100 million to $250 million, and expanded cover for infrastructure assets.
It also includes $10 million in new fine arts cover for Toitu Otago Settlers Museum's fine arts collection, which previously had only limited cover under the council's material damage policy.
That is despite total premiums dropping slightly, from $2.289 million in the past year to $2.109 million for 2015-16.
The details were reported to this week's council finance committee meeting by council group chief financial officer Grant McKenzie.
The new deal had been secured after Mr McKenzie flew to London earlier this year for two days of back-to-back meetings with international insurers from specialist insurance market Lloyds of London.
It was the second time Mr McKenzie had made the trip, but the initiative was delivering results, he told councillors.
The insurers responded to face-to-face meetings, which showed in the success rate of customers who came to see them, he said.
''They need to see you.''
The result came after the council was left with $2.3 billion of uninsured above and below-ground infrastructure assets following the Canterbury earthquakes.
That was after international reinsurers refused to cover underground assets and the council refused to pay inflated premiums for above-ground assets.
In a disaster, the council had to cover 40% of any damage bill to obtain the other 60% from central government.
The insurance gap prompted a review and Mr McKenzie's first trip to London last year, as he sought to play off international and domestic insurers and secure a better deal.
That led to an improved package, but this year's deal extended that while reducing the council's share of international cover slightly, from 35% to 30%, Mr McKenzie said.
Premiums for domestic insurance were slightly cheaper than international offerings but the council was running a ''long-term play'' by continuing to spread its risk, he told this week's meeting.
Having all the council's insurance eggs in one domestic basket risked large premium increases or other problems in the event of a major event, he said.
