Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands		Total	Common Stock		Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2009		$ 678,899	$ 379	[1]	$ 551,606	$ (9,221)	$ 136,358	$ (223)
Stock issued for benefit plans		1,513			242	1,271
Stock options exercised plans		2,087	1	[1]	2,086
Public stock offering plans		140,139	40	[1]	140,099
Purchase of treasury plans		(1,828)				(1,828)
Tax benefits from share-based compensation		28			28
Employee stock purchase plan plans		951	1	[1]	950
Issuance of restricted stock plans			3	[1]	(3)
Amortization of share-based compensation		11,849			11,849
Net Income		46,294					46,294
Other comprehensive income		85						85
Total comprehensive income		46,379
Ending Balance at Dec. 31, 2010		880,017	424	[1]	706,857	(9,778)	182,652	(138)
Stock issued for benefit plans	[2]	1,612			791	821
Stock options exercised plans	[2]	1,102	1	[1]	1,101
Purchase of treasury plans	[2]	(3,319)				(3,319)
Tax benefits from share-based compensation	[2]	329			329
Employee stock purchase plan plans	[2]	1,000	1	[1]	999
Issuance of restricted stock plans	[2]		4	[1]	(4)
Amortization of share-based compensation	[2]	12,429			12,429
Net Income	[2]	78,185					78,185
Other comprehensive income	[2]	138						138
Total comprehensive income	[2]	78,323
Ending Balance at Sep. 30, 2011	[2]	$ 971,493	$ 430	[1]	$ 722,502	$ (12,276)	$ 260,837	$ 0

[1] [1] $.01 par value.

[2] [2] Unaudited