CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Total
Balance at the beginning of the period at Dec. 31, 2014	$ 396	$ 2,838,013	$ (606,934)	$ (7,712)		$ 3,743	$ 2,227,506
Balance at the beginning of the period, shares at Dec. 31, 2014	39,638,094
Increase (Decrease) in Stockholders' Equity
Net income			100,838				100,838
Adjustment to noncontrolling interest						29	29
Interest rate swaps, net of tax				297			297
Capitalized swap interest, net of tax benefit				(154)			(154)
Stock plan activity	$ 2	7,008					7,010
Stock plan activity, shares	76,744
Balance at the end of the period at Sep. 30, 2015	$ 398	2,845,021	(506,096)	(7,569)		3,772	2,335,526
Balance at the end of the period, shares at Sep. 30, 2015	39,714,838
Balance at the beginning of the period at Dec. 31, 2015	$ 398	2,847,823	(480,215)	(7,889)		3,772	2,363,889
Balance at the beginning of the period, shares at Dec. 31, 2015	39,714,838
Increase (Decrease) in Stockholders' Equity
Net income			158,708			23	158,731
Preferred dividend payment on behalf of REIT subsidiary						(23)	(23)
Interest rate swaps, net of tax				(14,876)			(14,876)
Pension adjustment, net of tax				(890)			(890)
Capitalized swap interest, net of tax benefit				(163)			(163)
Stock plan activity		8,512					8,512
Stock plan activity, shares	136,198
Treasury stock activity					$ (1,295)		(1,295)
Treasury stock activity (in shares)					(12,061)
Balance at the end of the period at Sep. 30, 2016	$ 398	$ 2,856,335	$ (321,507)	$ (23,818)	$ (1,295)	$ 3,772	$ 2,513,885
Balance at the end of the period, shares at Sep. 30, 2016	39,851,036				(12,061)