Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements of Changes in Shareholders' Equity (Unaudited) [Abstract]
Balance	$ 1,149,484	$ 1,110,060
Net income per consolidated statements of income	55,615	49,616
Other comprehensive income:
Net change in fair value of securities available for sale	13,594	5,919
Net change in defined benefit plans	1,506	1,109
Comprehensive income	70,715	56,644
Common stock dividends paid	(29,740)	(29,642)
Common stock issued-net, long-term incentive plans:
Stock options	1,507	2,480
Restricted stock	(1,868)	(1,003)
Excess tax benefit from stock-based compensation arrangements	630	1,380
Compensation expense, long-term incentive plans	2,042	2,521
Other	0	(60)
Balance	$ 1,192,770	$ 1,142,380