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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Line Items]
Net income to shareholders	$ 149,660	$ 78,797	$ 219,529	$ 239,167
Adjustment of redeemable noncontrolling interests	(5,141)	(2,529)	(20,284)	(5,981)
Adjusted net income to shareholders	$ 144,519	$ 76,268	$ 199,245	$ 233,186
Basic common shares outstanding	13,977	14,012	13,987	14,003
Diluted shares outstanding	14,019	14,088	14,032	14,087
Basic net income per share	$ 10.34	$ 5.44	$ 14.25	$ 16.65
Diluted net income per share	$ 10.31	$ 5.41	$ 14.20	$ 16.55
Stock Options [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares	2	4	2	5
Restricted Stock Units (RSUs) [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares	40	72	43	79