Nomura has reiterated its buy rating and 630p target price on insurance giant Aviva, after its full-year results showed 'good earnings and improving solvency'.Full-year earnings were better than expected with IFRS operating profit of £2,503m beating consensus estimates of £2,414m and operational cash generation coming in well passed forecasts of £1.6bn at £2.1bn."The main drivers of this are operational jaws, with cash revenues increasing and new business strain and expenses falling," Nomura said.Solvency coverage of 135% was worse than the broker's 145% estimate, "however, Aviva has indicated that the solvency surplus rose to £3.3bn at February 29th, which takes solvency coverage to 152% (our estimate), which is a much more reassuring level of solvency coverage."Nomura remains a buyer of the stock, saying that Aviva is attractively valued - trading at 6.5 times 2012 earnings. However, Legal & General still remains its top UK pick in the sector given better growth opportunities and a lower risk profile with higher solvency.BC