Condensed Consolidated Statements of Redeemable Preferred Stock and Equity (Unaudited) (USD $) In Thousands, except Share data	Total	Preferred Stock And Common Stock	Common Class A	Common Class A Preferred Stock And Common Stock	Redeemable Preferred Stock	Redeemable Preferred Stock Preferred Stock And Common Stock	Common Stock	Common Stock Additional Paid in Capital	Common Stock Additional Paid in Capital Preferred Stock And Common Stock	Warrants Additional Paid in Capital	Warrants Additional Paid in Capital Preferred Stock And Common Stock	Retained Earnings	Treasury Stock
Beginning Balance at Dec. 31, 2011	$ 120,576		$ 1		$ 147,779			$ 80,747		$ 3,698		$ 36,528	$ (398)
Beginning Balance, Shares at Dec. 31, 2011			13,962,155		13,455,522		13,962,155
Derecognition of Series A Preferred Stock					(149,587)
Derecognition of Series A Preferred Stock, Shares					(13,455,522)
Stock issued during period	3,958	108,245		1		83,165		3,958	111,795		(3,551)
Stock issued during period, shares			319,301	7,660,612		2,999,493
Issuance of common stock in initial public offering, net of issue cost of $8,780	59,919						1	59,918
Stock issued during period shares initial public offering			(342,860)				7,200,000
Stock compensation expense	4,964							4,964
Accretion of Series A Preferred Stock to redemption value	(1,808)				1,808							(1,808)
Net income	14,017											14,017
Ending Balance at Mar. 31, 2012	309,871		2		83,165		1	261,382		147		48,737	(398)
Ending Balance, Shares at Mar. 31, 2012			21,599,208		2,999,493		7,200,000
Beginning Balance at Dec. 31, 2012	324,764				83,043		3	273,989		147		53,823	(3,198)
Beginning Balance, Shares at Dec. 31, 2012					2,995,106		30,559,935
Stock issued during period	423							423
Stock issued during period, shares	58,501						58,501
Stock compensation expense	1,356							1,356
Net income	46,403											46,403
Conversion of Sereis B preferred stock to common stock	32				(32)			32
Conversion of Sereis B preferred stock to common stock, shares					(1,140)		2,300
Conversion of restricted stock units to common stock (net of 21,675 shares of treasury stock purchased)	(158)												(158)
Conversion of restricted stock units to common stock (net of 21,675 shares of treasury stock purchased), shares	28,325						28,325
Ending Balance at Mar. 31, 2013	$ 372,820				$ 83,011		$ 3	$ 275,800		$ 147		$ 100,226	$ (3,356)
Ending Balance, Shares at Mar. 31, 2013					2,993,966		30,649,061