Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share Reconciliation [Abstract]
Weighted average number of common shares outstanding used in computing basic earnings per share	46,605	45,997	46,260	45,702
Net income attributable to common stockholders	$ 13,619	$ 8,553	$ 20,328	$ 20,077
Earnings per share attributable to common stockholders - basic	$ 0.29	$ 0.19	$ 0.44	$ 0.44
Weighted Average Number of Shares Outstanding, Basic, Total	46,605	45,997	46,260	45,702
Add: Assumed exercise of stock options and stock awards	1,418	998	1,324	1,199
Diluted shares	48,023	46,995	47,584	46,901
Net income attributable to common stockholders	$ 13,619	$ 8,553	$ 20,328	$ 20,077
Earnings per share attributable to common stockholders - diluted	$ 0.28	$ 0.18	$ 0.43	$ 0.43
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.