Investment Securities - Summary of Net Investment Income (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	3 Months Ended	12 Months Ended
Dec. 31, 2012 Successor [Member]	Mar. 19, 2012 Predecessor [Member]	Dec. 31, 2011 Predecessor [Member]	Dec. 31, 2010 Predecessor [Member]
Investment income:
Amortization of premium or discount on fixed-maturity	$ (1,837)	$ (523)	$ (2,750)	$ (2,822)
Investment income on fixed-maturity securities	7,232	2,467	12,920	17,410
Interest income on cash and equivalents	161	3	49	47
Realized net gain (loss) from sale of investment	2,747	176	1,206	4,796
Unrealized (losses) gains on trading securities held at period end	(1,410)	1,049	(2,828)	396
Net investment income	$ 6,893	$ 3,172	$ 8,597	$ 19,827

This item represents investment income derived from investments in debt and equity securities consisting of interest income earned from investments in debt securities and on cash and cash equivalents, dividend income from investments in equity securities, and income or expense derived from the amortization of investment related discounts or premiums, respectively, net of related investment expenses. This item does not include realized or unrealized gains or losses on the sale or holding of investments in debt and equity securities required to be included in earnings for the period or for other than temporary losses related to investments in debt and equity securities which are included in realized losses in the period recognized, and does not include investment income from real or personal property, such as rental income.

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This item represents the net amount of amortization of purchase discounts and premiums related to investments in debt securities. The purchase discount or premium is amortized to income or expense, respectively, over the life (holding period) of the securities to arrive at an amount of periodic interest income or expense which results in a constant effective yield on the investments.

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