Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Net unrealized gains (losses) on investments	$ 208,173	$ 377,322
Fixed Maturities [Member]
Net unrealized gains (losses) on investments	207,976	375,409
Equity Securities [Member]
Net unrealized gains (losses) on investments	2	4
Other Long-term Investments [Member]
Net unrealized gains (losses) on investments	78	46
Affiliated Notes [Member]
Net unrealized gains (losses) on investments	3,264	4,386
Securities Related to Other Than Temporary Impairments [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	359	545
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Net unrealized gains (losses) on investments	$ (3,506)	$ (3,068)