Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Net unrealized gains (losses) on investments	$ 329,168		$ 377,322
Fixed Maturities [Member]
Net unrealized gains (losses) on investments	326,121		375,409
Equity Securities [Member]
Net unrealized gains (losses) on investments	4		4
Other Long-term Investments [Member]
Net unrealized gains (losses) on investments	(69)		46
Affiliated Notes [Member]
Net unrealized gains (losses) on investments	4,069		4,386
Securities Related to Other Than Temporary Impairments [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	365		545
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Net unrealized gains (losses) on investments	$ (1,322)	[1]	$ (3,068)	[1]

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