Statements of Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (loss) [Member]	Total Equity
Balance at Dec. 31, 2010		$ 2,500	$ 974,921	$ 749,751	$ 181,212	$ 1,908,384
Affiliated asset transfers	0
Distribution to parent	270,000	0	0	(270,000)	0	(270,000)
Cumulative Effect Of Adoption Of New Accounting Principle		0	0	(127,920)	9,659	(118,261)
Comprehensive income:
Net income	(283,558)	0	0	(283,558)	0	(283,558)
Other comprehensive income (loss), net of tax	(35,842)	0	0	0	(35,842)	(35,842)
Balance at Sep. 30, 2011		2,500	974,921	68,273	155,029	1,200,723
Balance at Dec. 31, 2011		2,500	882,670	(25,305)	160,712	1,020,577
Affiliated asset transfers	10,666	0	10,666	0	0	10,666
Distribution to parent	248,000	0	0	(248,000)	0	(248,000)
Comprehensive income:
Net income	444,947	0	0	444,947	0	444,947
Other comprehensive income (loss), net of tax	5,548	0	0	0	5,548	5,548
Balance at Sep. 30, 2012		$ 2,500	$ 893,336	$ 171,642	$ 166,260	$ 1,233,738