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Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
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	$ 67,683
One to five years, Carrying Value	151,891
Five to ten years, Carrying Value	134,470
More than ten years, Carrying Value	134,032
Total, Carrying Value	573,688
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	68,316
One to five years, Fair Value	160,322
Five to ten years, Fair Value	149,054
More than ten years, Fair Value	142,699
Total, Fair Value	614,348
U.S. agency-based mortgage-backed securities [Member] | 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
Held-to-maturity, Amortized cost	30,077
U.S. agency-based mortgage-backed securities [Member] | 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
Held-to-maturity, Fair Value	32,886
Commercial mortgage-backed securities [Member] | 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
Held-to-maturity, Amortized cost	51,524
Commercial mortgage-backed securities [Member] | 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
Held-to-maturity, Fair Value	56,977
Asset-backed securities [Member] | 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
Held-to-maturity, Amortized cost	4,011
Asset-backed securities [Member] | 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
Held-to-maturity, Fair Value	$ 4,124

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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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