Summary of Operations and Significant Accounting Policies - Schedule of Earnings Per Share, Basic and Diluted (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic
Weighted average number of common shares outstanding used in computing basic earnings per share									47,184	46,363	45,780
Net income attributable to common stockholders	$ 16,665	$ 19,427	$ 17,385	$ 10,202	$ 6,204	$ 13,619	$ 8,635	$ (1,926)	$ 63,678	$ 26,532	$ 24,152
Basic earnings per share attributable to common stockholders	$ 0.35	$ 0.41	$ 0.37	$ 0.22	$ 0.13	$ 0.29	$ 0.19	$ (0.04)	$ 1.35	$ 0.57	$ 0.53
Diluted
Weighted average number of common shares outstanding used in computing basic earnings per share									47,184	46,363	45,780
Add: Assumed exercise of stock options and stock awards									1,410	1,295	1,119
Weighted average number of common shares outstanding used in computing diluted earnings per share									48,594	47,658	46,899
Net income attributable to common stockholders	$ 16,665	$ 19,427	$ 17,385	$ 10,202	$ 6,204	$ 13,619	$ 8,635	$ (1,926)	$ 63,678	$ 26,532	$ 24,152
Diluted earnings per share attributable to common stockholders	$ 0.34	$ 0.40	$ 0.36	$ 0.21	$ 0.13	$ 0.28	$ 0.18	$ (0.04)	$ 1.31	$ 0.56	$ 0.51