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	35,278			35,278
Other Comprehensive income:
Unrealized holding gain/(loss) arising during the period	1,903
Net gain recognized in other comprehensive income	966
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	36,244
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		54,921
Share-based compensation	1,679	0	1,679	0	0
Cash Dividends:
Cash dividends to common stockholders	(36,136)	0	0	(36,136)	0
Balance, value at June 30, 2012 at Jun. 30, 2012	$ 445,272	$ 278	$ 467,357	$ (30,510)	$ 8,147
Balance, shares at Jun. 30, 2012	27,806,129	27,806,129