Changes In Equity And Comprehensive Income (Summary Of Changes In Equity) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Changes In Equity And Comprehensive Income [Line Items]
Balance, beginning of period	$ 822,056
Net income (loss)	51,796	48,378
Other comprehensive income	22,817	31,638
Comprehensive income (loss)	74,613	80,016
Balance, end of period	895,856
Total Shareholders' Equity [Member]
Changes In Equity And Comprehensive Income [Line Items]
Balance, beginning of period	813,553	984,944
Dividends	(15,090)	(13,444)
Reacquisition of shares on open market		(29,999)
Exercise of stock options, net of shares reacquired	7,323	12,599
Stock compensation expense	4,007	3,503
Excess tax benefit from stock based compensation	2,947	3,952
Net income (loss)	51,662	48,467
Other comprehensive income	22,791	31,558
Comprehensive income (loss)	74,453	80,025
Balance, end of period	887,193	1,041,580
Total Equity [Member]
Changes In Equity And Comprehensive Income [Line Items]
Balance, beginning of period	822,056	993,030
Dividends	(15,090)	(13,444)
Reacquisition of shares on open market		(29,999)
Exercise of stock options, net of shares reacquired	7,323	12,599
Stock compensation expense	4,007	3,503
Excess tax benefit from stock based compensation	2,947	3,952
Net income (loss)	51,796	48,378
Other comprehensive income	22,817	31,638
Comprehensive income (loss)	74,613	80,016
Balance, end of period	895,856	1,049,657
Noncontrolling Interests [Member]
Changes In Equity And Comprehensive Income [Line Items]
Balance, beginning of period	8,503	8,086
Net income (loss)	134	(89)
Other comprehensive income	26	80
Comprehensive income (loss)	160	(9)
Balance, end of period	$ 8,663	$ 8,077