Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Consolidated Statements of Changes in Shareholders' Equity (Unaudited) [Abstract]
Balance, January 1,	$ 1,354,953	$ 1,287,369
Net income per consolidated statements of income	29,003	24,866
Other comprehensive income	5,234	2,314
Common stock dividends paid	(15,597)	(15,560)
Common stock issued-net, long-term incentive plans:
Stock options	0	109
Restricted stock	(792)	(938)
Excess tax (expense) benefit from stock-based compensation arrangements	(97)	269
Compensation expense, long-term incentive plans	1,191	1,022
Common stock issued, business combinations	0	53,495
Balance, March 31,	$ 1,373,895	$ 1,352,946