Consolidated Statements Of Changes In Stockholder's Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss), Net Of Deferred Income Taxes [Member]	Retained Earnings [Member]	Total
Balance, beginning of period, shares at Dec. 31, 2013	1,000
Balance, beginning of period at Dec. 31, 2013		$ 351,051	$ 87,648	$ 3,751,779
Share-based compensation plans		6,486
Net increase (decrease) during the period			42,480		$ 42,480
Net income (loss)				244,640	244,640
Balance, end of period, shares at Jun. 30, 2014	1,000
Balance, end of period at Jun. 30, 2014		357,537	130,128	3,996,419	4,484,084
Balance, beginning of period, shares at Mar. 31, 2014	1,000
Balance, beginning of period at Mar. 31, 2014		354,445	102,678	3,838,245
Share-based compensation plans		3,092
Net increase (decrease) during the period			27,450		27,450
Net income (loss)				158,174	158,174
Balance, end of period, shares at Jun. 30, 2014	1,000
Balance, end of period at Jun. 30, 2014		357,537	130,128	3,996,419	$ 4,484,084
Balance, beginning of period, shares at Dec. 31, 2014	1,000				1,000
Balance, beginning of period at Dec. 31, 2014		362,293	4,519	4,205,905	$ 4,572,717
Share-based compensation plans		6,991
Net increase (decrease) during the period			3,388		3,388
Net income (loss)				249,710	$ 249,710
Balance, end of period, shares at Jun. 30, 2015	1,000				1,000
Balance, end of period at Jun. 30, 2015		369,284	7,907	4,455,615	$ 4,832,806
Balance, beginning of period, shares at Mar. 31, 2015	1,000
Balance, beginning of period at Mar. 31, 2015		366,258	12,430	4,321,849
Share-based compensation plans		3,026
Net increase (decrease) during the period			(4,523)		(4,523)
Net income (loss)				133,766	$ 133,766
Balance, end of period, shares at Jun. 30, 2015	1,000				1,000
Balance, end of period at Jun. 30, 2015		$ 369,284	$ 7,907	$ 4,455,615	$ 4,832,806