Consolidated Statements of Shareholders' Equity (USD $) In Thousands, except Per Share data, unless otherwise specified	Total	Common Stock	Retained Earnings [Member]
Stockholders' Equity Attributable to Parent, Beginning of Period at Dec. 31, 2010	$ 506,214	$ 236,503	$ 269,711
Shares, Outstanding, Beginning of Period at Dec. 31, 2010		16,571
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings and comprehensive income	64,355		64,355
Issuance of common stock for convertible note payable, shares		453
Issuance of common stock for convertible note payable, value	16,669	16,669
Issuance of common stock for employee benefit plans, shares		24
Issuance of common stock for employee benefit plan, value	725	725
Issuance of common stock for long-term incentive plan, shares		103
Issuance of common stock for long-term incentive plan, value	1,929	1,929
Tax windfall/(shortfall) provision from share-based compensation	151	151
Repurchase of common stock, shares		(25)
Stock repurchased during period, value	(1,308)	(1,308)
Restricted stock forfeitures	0	(1)
Grant of restricted stock, shares		53
Amortization of restricted stock, value	4,377	4,377
Cash dividends	(10,110)		(10,110)
Restricted dividends	(125)		(125)
Stock option plan expense	1,153	1,153
Cash dividends, in dollars per share	$ 0.60
Restricted dividends, in dollars per share	$ 0.60
Stockholders' Equity Attributable to Parent, End of Period at Dec. 31, 2011	584,030	260,199	323,831
Shares, Outstanding, End of Period at Dec. 31, 2011		17,178
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings and comprehensive income	58,276		58,276
Issuance of common stock, stock option exercises, shares		155
Issuance of common stock, stock option exercises, value	5,663	5,663
Issuance of common stock for employee benefit plans, shares		19
Issuance of common stock for employee benefit plan, value	714	714
Issuance of common stock for long-term incentive plan, shares		158
Issuance of common stock for long-term incentive plan, value	4,207	4,207
Tax windfall/(shortfall) provision from share-based compensation	1,407	1,407
Repurchase of common stock, shares		(84)
Stock repurchased during period, value	(5,094)	(5,094)
Restricted stock forfeitures		(1)
Grant of restricted stock, shares		23
Amortization of restricted stock, value	6,377	6,377
Cash dividends	(12,351)		(12,351)
Restricted dividends	(170)		(170)
Stock option plan expense	1,236	1,236
Cash dividends, in dollars per share	$ 0.72
Restricted dividends, in dollars per share	$ 0.72
Stockholders' Equity Attributable to Parent, End of Period at Dec. 31, 2012	644,295	274,709	369,586
Shares, Outstanding, End of Period at Dec. 31, 2012		17,448
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings and comprehensive income	54,900		54,900
Issuance of common stock, stock option exercises, shares		7
Issuance of common stock, stock option exercises, value	330	330
Issuance of common stock for employee benefit plans, shares		17
Issuance of common stock for employee benefit plan, value	805	805
Issuance of common stock for long-term incentive plan, shares		174
Issuance of common stock for long-term incentive plan, value	6,371	6,371
Tax windfall/(shortfall) provision from share-based compensation	2,981	2,981
Repurchase of common stock, shares		(133)
Stock repurchased during period, value	(10,723)	(10,723)
Restricted stock forfeitures		(1)
Grant of restricted stock, shares		436
Amortization of restricted stock, value	20,525	20,525
Cash dividends	(15,186)		(15,186)
Restricted dividends	(466)		(466)
Stock option plan expense	957	957
Cash dividends, in dollars per share	$ 0.87
Restricted dividends, in dollars per share	$ 0.87
Stockholders' Equity Attributable to Parent, End of Period at Dec. 31, 2013	$ 704,789	$ 295,955	$ 408,834
Shares, Outstanding, End of Period at Dec. 31, 2013		17,948