16. Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 154,146	$ 349,318	$ 338,119	$ 382,286
Weighted-average common shares outstanding	103,339	100,906	102,496	100,713
Effect of restricted and performance stock units and stock purchase plan shares	394	1,393	566	1,132
Weighted-average shares used in computing diluted net income per share	103,733	102,299	103,062	101,845
Net income per share, basic	$ 1.49	$ 3.46	$ 3.30	$ 3.80
Net income per share, diluted	$ 1.49	$ 3.41	$ 3.28	$ 3.75
Anti-dilutive shares	411	46	282	64