Principal Accounting Policies (Calculation Of Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accounting Policies [Abstract]
Net Income	$ 30,557	$ 25,304	$ 87,459	$ 92,750
Weighted-average common shares outstanding	56,714,423	55,906,636	56,390,621	55,806,937
Stock options and nonvested stock	648,411	556,899	674,525	625,279
Denominator for net income per share	57,362,834	56,463,535	57,065,146	56,432,216
Diluted Earnings per Share:	$ 0.53	$ 0.45	$ 1.53	$ 1.64
Anit-dilutive securities excluded from the computation of diluted EPS	930,616	1,818,992	954,749	1,779,609