Earnings Per Share (Schedule Computing Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share [Abstract]
Net income/(loss) available to common shareholders	$ 47,041	$ 16,733
Weighted average number of shares used in calculating basic net income per share	31,309	31,223
Stock options	110	114
Long-term incentive plan	114	47
Weighted average number of shares used in calculating diluted net income per share	31,533	31,384
Effect of stock-based compensation plans that were not included in the computation of diluted earnings per share because to do so would have been antidilutive
Average market price of common stock used for calculation of dilutive shares	$ 23.97	$ 23.81
Basic	$ 1.5	$ 0.54
Diluted	$ 1.49	$ 0.53