Earnings Per Share (Details) (USD $) In Thousands, except Per 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 Reconciliation [Abstract]
Weighted average number of common shares outstanding used in computing basic earnings per share	46,148	45,642	46,085	45,551
Net income attributable to common stockholders	$ 8,635	$ 6,653	$ 6,709	$ 11,524
Earnings per share attributable to common stockholders - basic	$ 0.19	$ 0.15	$ 0.15	$ 0.25
Weighted Average Number of Shares Outstanding, Basic, Total	46,148	45,642	46,085	45,551
Add: Assumed exercise of stock options and stock awards	1,359	1,217	1,298	1,365
Diluted shares	47,507	46,859	47,383	46,916
Net income attributable to common stockholders	$ 8,635	$ 6,653	$ 6,709	$ 11,524
Earnings per share attributable to common stockholders - diluted	$ 0.18	$ 0.14	$ 0.14	$ 0.25
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.