Earnings per 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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings per Share [Line Items]
Net income	$ 19,182	$ 5,080	$ 34,669	$ 10,131
Basic weighted-average shares outstanding (in shares)	40,508,872	40,332,340	40,473,705	40,289,889
Diluted average common shares outstanding (in shares)	40,693,741	40,458,932	40,655,416	40,414,033
Basic net income per share (in shares)	$ 0.47	$ 0.13	$ 0.86	$ 0.25
Diluted net income per share (in shares)	$ 0.47	$ 0.13	$ 0.85	$ 0.25
Total anti-dilutive shares excluded from the calculation (in shares)	10,311	0	18,906	101,573
Performance shares [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)	107,391	31,725	109,258	32,739
Total anti-dilutive shares excluded from the calculation (in shares)	10,311	0	18,474	84,143
Restricted stock units [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)	70,089	72,048	65,319	70,505
Total anti-dilutive shares excluded from the calculation (in shares)	0	0	432	17,430
Stock options [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)	7,389	22,819	7,134	20,900