Condensed Financial Information of Registrant (Schedule Of Condensed Financial Information Of Registrant, Statements Of Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net income	$ 15,376	$ 39,570	$ (9,264)	$ 66,461	$ (17,382)	$ 66,201	$ (5,264)	$ 73,356	$ 112,143	$ 116,911	$ 191,164
Gains on hedging instrument									0	0	1,139
Other comprehensive income, before tax									0	0	1,139
Income tax expense related to gains on hedging instrument									0	0	399
Other comprehensive income, net of tax:									0	0	740
Comprehensive income									112,143	116,911	191,904
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income									112,143	116,911	191,164
Gains on hedging instrument									0	0	1,139
Other comprehensive income, before tax									0	0	1,139
Income tax expense related to gains on hedging instrument									0	0	399
Other comprehensive income, net of tax:									0	0	740
Comprehensive income									$ 112,143	$ 116,911	$ 191,904