Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Net unrealized gains (losses) on investments	$ 377,322		$ 439,937		$ 498,104
Fixed Maturities [Member]
Net unrealized gains (losses) on investments	375,409		436,812		498,517
Equity Securities [Member]
Net unrealized gains (losses) on investments	4		561		3,103
Other Long-term Investments [Member]
Net unrealized gains (losses) on investments	46		3		(5)
Affiliated Notes [Member]
Net unrealized gains (losses) on investments	4,386		5,263		5,511
Securities Related to Other Than Temporary Impairments [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	545		(1,740)		(6,560)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Net unrealized gains (losses) on investments	$ (3,068)	[1]	$ (962)	[1]	$ (2,462)	[1]

[1] (1) See Note 11 for more information on cash flow hedges.