Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017	$ 1,451,608	$ 1,182	$ 1,794,713	$ (344,287)
Balance (in shares) at Dec. 31, 2017		118,204
Comprehensive income
Net income	37,777			37,777
Change in fair value of interest rate swap, net of tax	(2,028)				$ (2,028)
Total comprehensive income	35,749			37,777	(2,028)
Retirement of common stock	(2,525)	$ (1)	(2,524)
Retirement of common stock (in shares)		(117)
Dividends declared on common stock	(51,533)			(51,533)
Restricted stock compensation, net of forfeitures	3,486		3,486
Restricted stock grants		$ 4	(4)
Restricted stock grants (in shares)		457
Cumulative effect of adoption of new accounting standard	(2,575)			(2,575)
Balance at Mar. 31, 2018	1,434,210	$ 1,185	1,795,671	(360,618)	$ (2,028)
Balance (in shares) at Mar. 31, 2018		118,544
Balance at Dec. 31, 2018	1,415,059	$ 1,187	1,807,202	(393,330)
Balance (in shares) at Dec. 31, 2018		118,674
Comprehensive income
Net income	49,340			49,340
Retirement of common stock	(3,070)	$ (1)	(3,069)
Retirement of common stock (in shares)		(143)
Dividends declared on common stock	(52,994)			(52,994)
Restricted stock compensation, net of forfeitures	3,812		3,812
Restricted stock grants		$ 5	(5)
Restricted stock grants (in shares)		521
Stock options exercised	207		207
Stock options exercised ( in shares)		16
Cumulative effect of adoption of new accounting standard	(29,940)			(29,940)
Balance at Mar. 31, 2019	$ 1,382,414	$ 1,191	$ 1,808,147	$ (426,924)
Balance (in shares) at Mar. 31, 2019		119,068