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, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting Policies [Abstract]
Net Income									$ 104,546	$ 88,443	$ 3,985
Weighted-average common shares outstanding									55,837,574	55,388,297	52,507,320
Stock options and nonvested stock									648,413	713,606	661,979
Denominator for net income per share									56,485,987	56,101,903	53,169,299
Diluted Earnings per Share	$ 0.21	$ 0.45	$ 0.74	$ 0.46	$ 0.41	$ 0.52	$ 0.52	$ 0.12	$ 1.85	$ 1.58	$ 0.07
Antidilutive securities excluded from the computation of diluted EPS									1,801,995	1,878,191	1,582,355