Summary of Significant Accounting Policies (Schedule Of Basic and Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, 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
Accounting Policies [Abstract]
Net Income	$ 22,175	$ 21,259	$ 25,840	$ 17,511	$ 25,981	$ 25,128	$ 30,680	$ 21,245	$ 86,785	$ 103,034	$ 102,757
Weighted average common shares outstanding									72,866	72,909	72,787
Dilutive effect of stock-based awards									562	544	438
Shares used in computing diluted earnings per share									73,428	73,453	73,225
Basic earnings per share	$ 0.31	$ 0.29	$ 0.35	$ 0.24	$ 0.36	$ 0.34	$ 0.42	$ 0.29	$ 1.19	$ 1.41	$ 1.41
Diluted earnings per share	$ 0.30	$ 0.29	$ 0.35	$ 0.24	$ 0.35	$ 0.34	$ 0.42	$ 0.29	$ 1.18	$ 1.40	$ 1.40
Number of antidilutive options that were excluded from computation of earnings per share									0	0	0