Consolidated statements of stockholders' equity Statement (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common stock	Additional paid in capital	Retained earnings (accumulated deficit)	Accumulated other comprehensive income
Stockholders' equity, balance at beginning of the period at Dec. 31, 2011	$ 424,013	$ 14	$ 419,370	$ (47,217)	$ 51,846
Balance at beginning of period (in shares) at Dec. 31, 2011	1,418,208	1,418,208
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock issuances	17,494	17,494
Restricted stock forfeited	(14,199)	(14,199)
Restricted stock repurchased		(1,469)
Stock-based compensation	3,064		3,064
Net income	64,403			64,403
Other comprehensive income (loss), net of tax	(28,623)				(28,623)
Stockholders' equity, balance at end of the period at Dec. 31, 2012	462,857	14	422,434	17,186	23,223
Balance at end of period (in shares) at Dec. 31, 2012	1,420,034	1,420,034
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock issuances	8,056	8,056
Restricted stock forfeited	(4,905)	(4,905)
Restricted stock repurchased		(1,025)
Stock-based compensation	1,943		1,943
Net income	55,687
Other comprehensive income (loss), net of tax	(23,223)				(23,223)
Stockholders' equity, balance at end of the period at Dec. 31, 2013	497,264	14	424,377	72,873	0
Balance at end of period (in shares) at Dec. 31, 2013	1,422,160	1,422,160
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock issuances	15,278	15,278
Restricted stock forfeited	(11,497)	(11,497)
Restricted stock repurchased		(2,025)
Stock-based compensation	5,301		5,301
Net income	209,293
Other comprehensive income (loss), net of tax	0
Stockholders' equity, balance at end of the period at Dec. 31, 2014	$ 711,858	$ 14	$ 429,678	$ 282,166	$ 0
Balance at end of period (in shares) at Dec. 31, 2014	1,423,916	1,423,916