Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 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	82,583	75,476
Other comprehensive income:
Net change in fair value of securities available for sale	28,779	9,561
Net change in defined benefit plans	2,253	1,711
Comprehensive income	113,615	86,748
Common stock dividends paid	(44,614)	(44,473)
Common stock issued-net, long-term incentive plans:
Stock options	1,507	2,480
Restricted stock	(1,867)	(1,008)
Excess tax benefit from stock-based compensation arrangements	553	1,357
Compensation expense, long-term incentive plans	2,928	3,688
Other	0	(60)
Balance	$ 1,221,606	$ 1,158,792