Note 1. Principal Accounting Policies Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 44,035	$ 53,667	$ 65,827	$ 66,560
Weighted average common shares outstanding - Basic	57,419,971	57,128,379	57,526,585	57,043,378
Stock options and nonvested stock	385,383	566,312	486,584	533,995
Weighted average common shares outstanding - Diluted	57,805,354	57,694,691	58,013,169	57,577,373
Diluted EPS	$ 0.76	$ 0.93	$ 1.13	$ 1.16
Anti-dilutive securities excluded from computation of diluted EPS	408,097	499,469	347,574	719,958