Condensed Consolidated Statement Of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Cumulative Dividends In Excess Of Net Income [Member]	Unrealized Gains On Marketable Securities [Member]
Balance, value at Dec. 31, 2011 at Dec. 31, 2011	$ 443,485	$ 278	$ 465,678	$ (29,652)	$ 7,181
Balance, shares at Dec. 31, 2011	27,751,208	27,751,208
Comprehensive income:
Net income	18,350			18,350
Other Comprehensive income:
Unrealized holding gain/(loss) arising during the period	408
Net gain recognized in other comprehensive income	408
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	18,758
Shares issued on stock options exercised, value	0	0	0	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		34,978
Share-based compensation	1,432	0	1,432	0	0
Cash Dividends:
Cash dividends to common stockholders	18,061	0	0	18,061	0
Balance, value at March 31, 2012 at Mar. 31, 2012	$ 445,614	$ 278	$ 467,110	$ (29,363)	$ 7,589
Balance, shares at Mar. 31, 2012	27,786,186	27,786,186