Consolidated Statements Of Changes In Stockholder's Equity (USD $) In Thousands, except Share data	Common Stock [Member]	Additional Paid-In Capital [Member] USD ($)	Accumulated Other Comprehensive Income (Loss), Net Of Deferred Income Taxes [Member] USD ($)	Retained Earnings [Member] USD ($)	Total USD ($)
Balance, beginning of period at Dec. 31, 2011		$ 333,416	$ 174,790	$ 2,433,187
Balance, beginning of period, shares at Dec. 31, 2011	1,000
Share-based compensation plans		6,807
Net increase (decrease) during the period			10,077		10,077
Net income (loss)				520,329	520,329
Balance, end of period at Dec. 31, 2012		340,223	184,867	2,953,516	3,478,606
Balance, end of period, shares at Dec. 31, 2012	1,000
Share-based compensation plans		10,828
Net increase (decrease) during the period			(97,219)		(97,219)
Net income (loss)				798,263	798,263
Balance, end of period at Dec. 31, 2013		351,051	87,648	3,751,779	4,190,478
Balance, end of period, shares at Dec. 31, 2013	1,000				1,000
Share-based compensation plans		11,242
Net increase (decrease) during the period			(83,129)		(83,129)
Net income (loss)				454,126	454,126
Balance, end of period at Dec. 31, 2014		$ 362,293	$ 4,519	$ 4,205,905	$ 4,572,717
Balance, end of period, shares at Dec. 31, 2014	1,000				1,000