Earnings per Common Share (Reconciliation Of Number Of Common Shares Used In Calculating Basic And Diluted EPS) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings per Share [Line Items]
Net income	$ 18,599	$ 25,599	$ 28,730	$ 41,744
Basic weighted-average shares outstanding (in shares)	40,356,512	40,187,334	40,316,957	40,147,133
Diluted average common shares outstanding (in shares)	40,571,068	40,380,302	40,503,158	40,359,877
Basic net income per share (in shares)	$ 0.46	$ 0.64	$ 0.71	$ 1.04
Diluted net income per share (in shares)	$ 0.46	$ 0.63	$ 0.71	$ 1.03
Total anti-dilutive shares excluded from the calculation (in shares)	0	77,767	1,000	80,467
Common stock options [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)	27,558	44,147	20,263	54,048
Performance shares [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)	119,400	120,182	102,000	129,691
Total anti-dilutive shares excluded from the calculation (in shares)	0	77,767	0	77,767
Restricted stock units [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)	67,598	28,639	63,938	29,005
Total anti-dilutive shares excluded from the calculation (in shares)	0	0	1,000	2,700