Earnings Per Share (Tables)

6 Months Ended

Jun. 30, 2018

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

The following table sets forth the computation of basic and diluted earnings per share on net income (in thousands, except per share information):



	Three months ended June 30,				Six months ended June 30,
	2018		2017		2018		2017
Earnings:
Net income (numerator for basic and diluted calculations)	$	204,374	$	232,190	$	304,604	$	377,702
Shares:
Weighted average outstanding shares (denominator for basic calculation)	64,071		64,449		64,278		64,401
Equivalent shares from outstanding stock options	1,179		1,159		1,277		1,204
Denominator for diluted calculation	65,250		65,608		65,555		65,605
Earnings per share:
Basic	$	3.19	$	3.60	$	4.74	$	5.86
Diluted	$	3.13	$	3.54	$	4.65	$	5.76

Schedule Of Earnings Per Share Basic And Diluted By Common Class [Text Block]

The following table presents approximate amounts of stock options and performance contingent shares excluded from the calculation of common equivalent shares (in millions):



	Three months ended June 30,		Six months ended June 30,
	2018	2017	2018	2017
Excluded from common equivalent shares:
Stock options	0.2	0.2	0.3	0.3
Performance contingent shares	0.2	0.3	0.2	0.3