Unaudited Condensed Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock	Paid-in Capital	Retained Earnings Substantially Restricted	Accumulated Other Comprehensive Income
Balance, beginning at Dec. 31, 2011	$ 850,227	$ 719	$ 642,882	$ 173,139	$ 33,487
Balance, beginning, shares at Dec. 31, 2011		71,915,073
Net income	54,758			54,758
Comprehensive income (loss), accumulated other comprehensive income	14,369				14,369
Comprehensive income, total	69,127
Cash dividends declared	(28,052)			(28,052)
Stock issuances under stock incentive plans, shares		22,149
Stock issuances under stock incentive plans, value	323	0	323
Stock-based compensation and related taxes	(1,468)		(1,468)
Balance, ending at Sep. 30, 2012	890,157	719	641,737	199,845	47,856
Balance, ending, shares at Sep. 30, 2012		71,937,222
Balance, beginning at Dec. 31, 2012	900,949	719	641,737	210,531	47,962
Balance, beginning, shares at Dec. 31, 2012	71,937,222	71,937,222
Net income	69,098			69,098
Comprehensive income (loss), accumulated other comprehensive income	(37,979)				(37,979)
Comprehensive income, total	31,119
Cash dividends declared	(32,299)			(32,299)
Stock issuances under stock incentive plans, shares		227,597
Stock issuances under stock incentive plans, value	3,502	2	3,500
Stock issued in connection with acquisitions, shares		2,143,132
Stock issued in connection with acquisitions, value	45,034	22	45,012
Stock-based compensation and related taxes	(498)		(498)
Balance, ending at Sep. 30, 2013	$ 947,807	$ 743	$ 689,751	$ 247,330	$ 9,983
Balance, ending, shares at Sep. 30, 2013	74,307,951	74,307,951