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, 2013		$ 351,051	$ 87,648	$ 3,751,779
Balance, beginning of period, shares at Dec. 31, 2013	1,000
Share-based compensation plans		3,394
Net increase (decrease) during the period			15,030		15,030
Net income (loss)				86,466	86,466
Balance, end of period at Mar. 31, 2014		354,445	102,678	3,838,245	4,295,368
Balance, end of period, shares at Mar. 31, 2014	1,000
Balance, beginning of period at Dec. 31, 2014		362,293	4,519	4,205,905	4,572,717
Balance, beginning of period, shares at Dec. 31, 2014	1,000				1,000
Share-based compensation plans		3,965
Net increase (decrease) during the period			7,911		7,911
Net income (loss)				115,944	115,944
Balance, end of period at Mar. 31, 2015		$ 366,258	$ 12,430	$ 4,321,849	$ 4,700,537
Balance, end of period, shares at Mar. 31, 2015	1,000				1,000