Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Carrying Value [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Less than one year, Carrying Value	$ 84,868
One to five years, Carrying Value	158,940
Five to ten years, Carrying Value	135,868
More than ten years, Carrying Value	136,330
Total, Carrying Value	607,681
Carrying Value [Member] \| U.S. agency-based mortgage-backed securities [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Held-to-maturity, Carrying Value	35,666
Carrying Value [Member] \| Commercial mortgage-backed securities [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Held-to-maturity, Carrying Value	51,535
Carrying Value [Member] \| Asset-backed securities [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Held-to-maturity, Carrying Value	4,474
Fair Value [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Less than one year, Fair Value	85,406
One to five years, Fair Value	168,395
Five to ten years, Fair Value	151,719
More than ten years, Fair Value	146,827
Total, Fair Value	654,175
Fair Value [Member] \| U.S. agency-based mortgage-backed securities [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Held-to-maturity, Fair Value	39,286
Fair Value [Member] \| Commercial mortgage-backed securities [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Held-to-maturity, Fair Value	58,208
Fair Value [Member] \| Asset-backed securities [Member]
Summary of the cost or amortized cost and fair value of investments in fixed maturity securities, classified as held-to-maturity, by contractual maturity
Held-to-maturity, Fair Value	$ 4,334

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Amount of held-to-maturity debt securities at fair value maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year.

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Amount of held-to-maturity debt securities at fair value maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year.

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