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, 2012	$ 900,949	$ 719	$ 641,737	$ 210,531	$ 47,962
Balance, beginning, shares at Dec. 31, 2012		71,937,222
Net income	20,768			20,768
Comprehensive income, accumulated other comprehensive income	2,113				2,113
Comprehensive income, total	22,881
Cash dividends declared	(10,099)			(10,099)
Stock issuances under stock incentive plans, shares		81,395
Stock issuances under stock incentive plans, value	1,266	1	1,265
Stock-based compensation and related taxes	(717)		(717)
Balance, ending at Mar. 31, 2013	914,280	720	642,285	221,200	50,075
Balance, ending, shares at Mar. 31, 2013		72,018,617
Balance, beginning at Dec. 31, 2013	963,250	744	690,918	261,943	9,645
Balance, beginning, shares at Dec. 31, 2013	74,373,296	74,373,296
Net income	26,730			26,730
Comprehensive income, accumulated other comprehensive income	5,643				5,643
Comprehensive income, total	32,373
Cash dividends declared	(11,942)			(11,942)
Stock issuances under stock incentive plans, shares		92,370
Stock issuances under stock incentive plans, value	1,037	1	1,036
Stock-based compensation and related taxes	242		242
Balance, ending at Mar. 31, 2014	$ 984,960	$ 745	$ 692,196	$ 276,731	$ 15,288
Balance, ending, shares at Mar. 31, 2014	74,465,666	74,465,666