Investments (Details 6) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	$ (71)	$ (218)	$ (71)	$ (1,424)
Net impairment losses recognized in earnings	(71)	(419)	(71)	(1,625)
Gross realized gains, available-for-sale securities	3,809	2,262	6,923	6,150
Gross realized (losses), available-for-sale securities	(890)	(89)	(965)	(183)
Net realized gains (losses), trading securities	6,043	(50)	8,832	727
Change in unrealized holding gains (losses), trading securities	(420)	(3,032)	20,432	4,905
Decrease (increase) in the fair value of liabilities carried at fair value	0	(220)	0	(844)
Total net realized investment gains (losses)	8,471	(1,548)	35,151	9,130
US States and Political Subdivisions Debt Securities [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	(71)	0	(71)	0
Residential mortgage-backed securities [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	0	(218)	0	(463)
Portion Of OTTI Losses Recognized In Reclassified From Other Comprehensive Income Before Taxes	0	(201)	0	(201)
Corporate debt [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	0	0	0	(830)
Other investments [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	$ 0	$ 0	$ 0	$ (131)

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