Principal Accounting Policies (Calculation Of Numerator And Denominator In Earnings Per Share) (Details) (USD $) In Thousands, except 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									$ 99,153	$ 104,546	$ 88,443
Weighted-average common shares outstanding									56,511,563	55,837,574	55,388,297
Stock options and nonvested stock									729,025	648,413	713,606
Denominator for net income per share									57,240,588	56,485,987	56,101,903
Diluted Earnings per Share	$ 0.20	$ 0.53	$ 0.75	$ 0.25	$ 0.21	$ 0.45	$ 0.74	$ 0.46	$ 1.73	$ 1.85	$ 1.58
Antidilutive securities excluded from the computation of diluted EPS									911,041	1,801,995	1,878,191