Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements of Changes in Shareholders' Equity
Total shareholders' equity at beginning of period	$ 2,061,680	$ 1,894,424
Comprehensive income:
Net income	107,614	100,718
Other comprehensive income	48,339	61,559
Total comprehensive income	155,953	162,277
Stock option exercises/deferred stock unit conversions (144,203 shares in 2011 and 491,728 shares in 2010)	7,239	23,172
Stock compensation expense recognized in earnings	7,583	7,058
Tax benefits related to stock compensation	278	277
Purchase of treasury stock (29,823 shares in 2011 and 3,406 shares in 2010)	(1,657)	(193)
Treasury stock issued/sold to the 401(k) stock purchase plan (40,019 shares in 2010)		2,069
Common stock issued/sold to the 401(k) stock purchase plan (22,680 shares in 2011 and 89,743 shares in 2010)	1,360	4,977
Cash dividends ($0.91 per share in 2011 and $0.88 per share in 2010)	(55,791)	(53,210)
Total shareholders' equity at end of period	$ 2,176,645	$ 2,040,851