Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	(Accumulated Deficit) Retained Earnings
BALANCE (in shares) at Dec. 31, 2014		116,764
BALANCE at Dec. 31, 2014	$ 1,481,500	$ 1,168	$ 1,748,303	$ (267,971)
Net income	122,580			122,580
Retirement of common stock (in shares)		(235)
Retirement of common stock	(9,432)	$ (3)	(9,429)
Dividends declared on common stock	(127,310)			(127,310)
Restricted stock compensation, net of forfeitures (in shares)		(6)
Restricted stock compensation, net of forfeitures	7,233		7,188	45
Income tax benefit of equity compensation	475		475
Stock option compensation expense, net of forfeitures	475		475
Restricted stock grants (in shares)		296
Restricted stock grants	3	$ 3
Stock options exercised (in shares)		300
Stock options exercised	5,637	$ 3	5,634
BALANCE (in shares) at Jun. 30, 2015		117,119
BALANCE at Jun. 30, 2015	1,481,161	$ 1,171	1,752,646	(272,656)
BALANCE (in shares) at Dec. 31, 2015		117,232
BALANCE at Dec. 31, 2015	1,462,748	$ 1,172	1,762,394	(300,818)
Net income	103,890			103,890
Retirement of common stock (in shares)		(134)
Retirement of common stock	(3,947)	$ (1)	(3,946)
Dividends declared on common stock	(127,998)			(127,998)
Restricted stock compensation, net of forfeitures (in shares)		(1)
Restricted stock compensation, net of forfeitures	7,777		7,720	57
Income tax benefit of equity compensation	25		25
Stock option compensation expense, net of forfeitures	96		96
Restricted stock grants (in shares)		310
Restricted stock grants	3	$ 3
Stock options exercised (in shares)		113
Stock options exercised	2,033	$ 1	2,032
BALANCE (in shares) at Jun. 30, 2016		117,520
BALANCE at Jun. 30, 2016	$ 1,444,627	$ 1,175	$ 1,768,321	$ (324,869)