Consolidated Statements of Changes in Shareholders’ Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Retained Earnings (Deficit)	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2011	$ 1,404,608	$ 723	$ 1,400,090	$ 191,476	$ (187,681)
Beginning Balance (in shares) at Dec. 31, 2011		72,258,472
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares to stockholders, directors and employees		2	(2)
Issuance of common shares to stockholders, directors and employees (in shares)		270,412
Repurchase of common shares from directors and employees	(44,180)	(39)	(44,141)
Repurchase of common shares from directors and employees (in shares)		(3,889,155)
Amortization of share based payments	4,232		4,232
Excess tax benefit from stock based compensation			376
Dividends declared	(43,669)			(43,669)
Net income	32,868			32,868
Net change in fair value of derivatives, net of tax expense of $586, $482 and $828, respectively	30,614				30,614
Net derivative loss reclassified into earnings	30,777				30,777
Beginning Balance at Dec. 31, 2012	1,415,626	686	1,360,555	180,675	(126,290)
Beginning Balance (in shares) at Dec. 31, 2012		68,639,729
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares to stockholders, directors and employees	205,258	128	205,130
Issuance of common shares to stockholders, directors and employees (in shares)		12,796,051
Repurchase of common shares from directors and employees	(7,821)	(6)	(7,815)
Repurchase of common shares from directors and employees (in shares)		(628,805)
Amortization of share based payments	4,569		4,569
Excess tax benefit from stock based compensation	(333)		(333)
Dividends declared	(52,058)			(52,058)
Net income	29,781			29,781
Net change in fair value of derivatives, net of tax expense of $586, $482 and $828, respectively	17,120				17,120
Net derivative loss reclassified into earnings	33,265				33,265
Beginning Balance at Dec. 31, 2013	1,645,407	808	1,562,106	158,398	(75,905)
Beginning Balance (in shares) at Dec. 31, 2013	80,806,975	80,806,975
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares to stockholders, directors and employees		4	(4)
Issuance of common shares to stockholders, directors and employees (in shares)		354,547
Repurchase of common shares from directors and employees	(2,092)	(2)	(2,090)
Repurchase of common shares from directors and employees (in shares)		(178,273)
Amortization of share based payments	4,244		4,244
Excess tax benefit from stock based compensation	924		924
Dividends declared	(66,421)			(66,421)
Net income	100,828			100,828
Net change in fair value of derivatives, net of tax expense of $586, $482 and $828, respectively	2,466				2,466
Net derivative loss reclassified into earnings	34,979				(34,979)
Beginning Balance at Dec. 31, 2014	$ 1,720,335	$ 810	$ 1,565,180	$ 192,805	$ (38,460)
Beginning Balance (in shares) at Dec. 31, 2014	80,983,249	80,983,249