Consolidated Statements Of Comprehensive Income (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
Statement of Comprehensive Income [Abstract]
Net income	$ 15,376	$ 39,570	$ (9,264)	$ 66,461	$ (17,382)	$ 66,201	$ (5,264)	$ 73,356	$ 112,143	$ 116,911	$ 191,164
Other comprehensive income, before tax:
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