Statements Of Equity (USD $) In Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2010	$ 2,500	$ 974,921	$ 621,831	$ 190,872	$ 1,790,124
Net income			121,521		121,521
Other comprehensive loss, net of taxes				(33,511)	(33,511)
Balance at Mar. 31, 2011	2,500	974,921	743,352	157,361	1,878,134
Balance at Dec. 31, 2011	2,500	882,670	(25,305)	160,712	1,020,577
Net income			372,347		372,347
Contributed capital - parent/child asset transfer		10,641			10,641
Other comprehensive loss, net of taxes				(13,562)	(13,562)
Balance at Mar. 31, 2012	$ 2,500	$ 893,311	$ 347,042	$ 147,150	$ 1,390,003