Shareholders' Equity (Schedule Of Net Income Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Line Items]
Net income to shareholders	$ 117,595	$ 75,803	$ 40,068	$ 87,716	$ 98,764	$ 65,599	$ 27,756	$ 88,902	$ 56,792	$ 49,653	$ 89,687	$ 57,253	$ 321,182	$ 281,021	$ 253,385
Adjustment of redeemable noncontrolling interests													(8,186)	1,963	(3,101)
Adjusted net income to shareholders													$ 312,996	$ 282,984	$ 250,284
Basic common shares outstanding													13,984	12,538	9,640
Diluted shares outstanding													14,057	12,586	9,666
Basic net income per share (dollars per share)	$ 8.10	$ 5.33	$ 2.67	$ 6.28	$ 6.98	$ 4.69	$ 2.24	$ 9.53	$ 6.25	$ 5.33	$ 8.44	$ 5.94	$ 22.38	$ 22.57	$ 25.96
Diluted net income per share (dollars per share)	$ 8.05	$ 5.30	$ 2.66	$ 6.25	$ 6.95	$ 4.67	$ 2.24	$ 9.50	$ 6.23	$ 5.32	$ 8.42	$ 5.92	$ 22.27	$ 22.48	$ 25.89
Stock Options [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares													11	12	6
Restricted Stock Units (RSUs) [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares													62	36	20