Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
BASIC
Weighted average number of common shares outstanding used in computing basic earnings per share	47,548	46,605	47,047	46,260
Net income attributable to common stockholders	$ 19,427	$ 13,619	$ 47,014	$ 20,328
Earnings per share attributable to common stockholders	$ 0.41	$ 0.29	$ 1.00	$ 0.44
DILUTED
Weighted average number of common shares outstanding used in computing basic earnings per share	47,548	46,605	47,047	46,260
Add: Dilutive effect of stock options and stock awards outstanding	1,188	1,418	1,338	1,324
Diluted shares	48,736	48,023	48,385	47,584
Net income attributable to common stockholders	$ 19,427	$ 13,619	$ 47,014	$ 20,328
Earnings per share attributable to common stockholders	$ 0.40	$ 0.28	$ 0.97	$ 0.43