CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning balance - Value at Dec. 31, 2009	$ 481,360	$ 359	$ 326,224	$ 148,620	$ (8)	$ 6,165
Beginning balance - Shares at Dec. 31, 2009		35,919,941			(417)
Comprehensive income:
Net income	37,187			37,187
Change in unrealized gain on available-for-sale securities, net of taxes of $100 (unaudited)	(810)					(810)
Total comprehensive income (unaudited)	36,377
Tax expense related to exercise of stock options	621		621
Stock-based compensation expense recognized in earnings	6,770		6,770
Issuance of stock related to stock-based awards - Value	866	3	863
Issuance of stock related to stock-based awards - Shares		302,328
Issuance of stock - Value	12,477	7	12,470
Issuance of stock - Shares		734,835
Purchase of non-controlling interest in bank owned subsidary	(10,152)		(10,152)
Ending balance (unaudited) - Value at Dec. 31, 2010	528,319	369	336,796	185,807	(8)	5,355
Ending balance (unaudited) - Shares at Dec. 31, 2010		36,957,104
Comprehensive income:
Net income	75,976			75,976
Change in unrealized gain on available-for-sale securities, net of taxes of $100 (unaudited)	(633)					(633)
Total comprehensive income (unaudited)	75,343
Tax expense related to exercise of stock options	3,139		3,139
Stock-based compensation expense recognized in earnings	7,340		7,340
Issuance of stock related to stock-based awards - Value	2,190	7	2,183
Issuance of stock related to stock-based awards - Shares		709,604
Ending balance (unaudited) - Value at Dec. 31, 2011	616,331	376	349,458	261,783	(8)	4,722
Ending balance (unaudited) - Shares at Dec. 31, 2011		37,666,708			(417)
Comprehensive income:
Net income	120,672			120,672
Change in unrealized gain on available-for-sale securities, net of taxes of $100 (unaudited)	(1,450)					(1,450)
Total comprehensive income (unaudited)	119,222
Tax expense related to exercise of stock options	7,769		7,769
Stock-based compensation expense recognized in earnings	5,578		5,578
Issuance of stock related to stock-based awards - Value	355	8	347
Issuance of stock related to stock-based awards - Shares		761,288
Issuance of stock - Value	86,987	23	86,964
Issuance of stock - Shares		2,300,000
Ending balance (unaudited) - Value at Jun. 30, 2012	$ 836,242	$ 407	$ 450,116	$ 382,455	$ (8)	$ 3,272
Ending balance (unaudited) - Shares at Jun. 30, 2012		40,727,996			(417)