Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Net unrealized gains (losses) on investments	$ 397,214		$ 439,937
Other Long-term Investments [Member]
Net unrealized gains (losses) on investments	4		3
Affiliated Notes [Member]
Net unrealized gains (losses) on investments	4,832		5,263
Available-for-sale Securities [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	391,063		436,812
Available-for-sale Securities [Member] | Equity Securities [Member]
Net unrealized gains (losses) on investments	689		561
Securities Related to Other Than Temporary Impairments [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	522		(1,740)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Net unrealized gains (losses) on investments	$ 104	[1]	$ (962)	[1]

[1] (1) See Note 5 for more information on cash flow hedges.