Earnings Per Share (Details) (USD $) In Thousands, except Per 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 Reconciliation [Abstract]
Weighted average number of common shares outstanding used in computing basic earnings per share	45,997	45,603	45,702	45,252
Net income attributable to common stockholders	$ 8,553	$ 9,957	$ 20,077	$ 47,622
Earnings per share attributable to common stockholders - basic	$ 0.19	$ 0.22	$ 0.44	$ 1.05
Weighted average number of common shares outstanding used in computing basic earnings per share	45,997	45,603	45,702	45,252
Add: Assumed exercise of stock options and stock awards	998	1,490	1,199	1,623
Diluted shares	46,995	47,093	46,901	46,875
Net income attributable to common stockholders	$ 8,553	$ 9,957	$ 20,077	$ 47,622
Earnings per share attributable to common stockholders - diluted	$ 0.18	$ 0.21	$ 0.43	$ 1.02
Earnings Per Share Reconciliation Disclosure			Basic earnings per share is calculated by dividing net earnings by the weighted-average number of shares of Common Stock outstanding during the period. Diluted earnings per share is calculated similarly but includes potential dilution from the exercise of stock options and stock awards, except when the effect would be anti-dilutive.