Consolidated 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, 2011			$ 836,021	$ 1,743,291	$ 213,628	$ 2,795,440
Affiliated asset transfers			(10,196)			(10,196)
Comprehensive income:
Net income	423,540			423,540		423,540
Other comprehensive income (loss), net of tax	59,600	0	0	0	59,600	59,600
Total comprehensive income (loss)						483,140
Balance at Sep. 30, 2012		2,500	825,825	2,166,831	273,228	3,268,384
Balance at Dec. 31, 2012		2,500	818,303	2,427,628	267,461	3,515,892
Affiliated asset transfers		0	(14,066)	0	0
Contributed Distributed Capital Parent Child Asset Transfers						(14,066)
Dividend To Parent				(155,000)		(155,000)
Comprehensive income:
Net income	1,236,698	0	0	1,236,698	0	1,236,698
Other comprehensive income (loss), net of tax	(189,452)				(189,452)	(189,452)
Total comprehensive income (loss)						1,047,246
Balance at Sep. 30, 2013		$ 2,500	$ 804,237	$ 3,509,326	$ 78,009	$ 4,394,072