Net Income Per Share (Schedule Of Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Line Items]
Net income to shareholders	$ 78,797	$ 91,369	$ 239,167	$ 282,361
Adjustment of redeemable noncontrolling interests	(2,529)	3,062	(5,981)	1,715
Adjusted net income to shareholders	$ 76,268	$ 94,431	$ 233,186	$ 284,076
Basic common shares outstanding	14,012	13,975	14,003	13,973
Diluted shares outstanding	14,088	14,052	14,087	14,057
Basic net income per share	$ 5.44	$ 6.76	$ 16.65	$ 20.33
Diluted net income per share	$ 5.41	$ 6.72	$ 16.55	$ 20.21
Stock Options [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares	4	9	5	10
Restricted Stock Units (RSUs) [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares	72	68	79	74