Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (USD $) In Thousands, except Share data	Total	Common Stock	Paid-in Capital	Retained Earnings Substantially Restricted	Accumulated Other Comprehensive Income
Balance at Dec. 31, 2010	$ 838,204	$ 719	$ 643,894	$ 193,063	$ 528
Balance, shares at Dec. 31, 2010		71,915,073
Comprehensive income, retained earnings substantially restricted	3,123			3,123
Comprehensive income, accumulated other comprehensive income	39,122				39,122
Comprehensive income, total	42,245
Cash dividends declared ($0.39 per share)	(28,047)			(28,047)
Stock-based compensation and related taxes	(1,014)		(1,014)
Balance at Sep. 30, 2011	851,388	719	642,880	168,139	39,650
Balance, shares at Sep. 30, 2011		71,915,073
Balance at Dec. 31, 2011	850,227	719	642,882	173,139	33,487
Balance, shares at Dec. 31, 2011	71,915,073	71,915,073
Comprehensive income, retained earnings substantially restricted	54,758			54,758
Comprehensive income, accumulated other comprehensive income	14,369				14,369
Comprehensive income, total	69,127
Cash dividends declared ($0.39 per share)	(28,052)			(28,052)
Stock issuances under stock incentive plans, shares		22,149
Stock issuances under stock incentive plans, value	323		323
Stock-based compensation and related taxes	(1,468)		(1,468)
Balance at Sep. 30, 2012	$ 890,157	$ 719	$ 641,737	$ 199,845	$ 47,856
Balance, shares at Sep. 30, 2012	71,937,222	71,937,222