CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Common Stock and Additional Paid-in Capital	Retained Earnings	Treasury Stock	AOCI, net of tax
Beginning balance (in shares) at Dec. 31, 2014		143,582,229
Beginning balance at Dec. 31, 2014	$ 2,856,111		$ 1,677,931	$ 1,604,141	$ (430,198)	$ 4,237
Increase (Decrease) in Stockholders' Equity
Net income	292,872			292,872
Other comprehensive loss	(2,407)					(2,407)
Stock compensation costs	11,702		11,702
Tax benefit from stock compensation plans, net	3,227		3,227
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)		287,725
Net activity of common stock pursuant to various stock compensation plans and agreements	(3,290)		2,569		(5,859)
Common stock dividends	(87,100)			(87,100)
Ending balance (in shares) at Sep. 30, 2015		143,869,954
Ending balance at Sep. 30, 2015	3,071,115		1,695,429	1,809,913	(436,057)	1,830
Beginning balance at Jun. 30, 2015						5,430
Increase (Decrease) in Stockholders' Equity
Net income	94,097
Other comprehensive loss	(3,600)					(3,600)
Tax benefit from stock compensation plans, net	31
Ending balance (in shares) at Sep. 30, 2015		143,869,954
Ending balance at Sep. 30, 2015	3,071,115		1,695,429	1,809,913	(436,057)	1,830
Beginning balance (in shares) at Dec. 31, 2015		143,909,233
Beginning balance at Dec. 31, 2015	3,122,950		1,701,459	1,872,594	(436,162)	(14,941)
Increase (Decrease) in Stockholders' Equity
Net income	320,943			320,943
Other comprehensive loss	7,767					7,767
Stock compensation costs	13,973		13,973
Tax benefit from stock compensation plans, net	1,019		1,019
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)		224,071
Net activity of common stock pursuant to various stock compensation plans and agreements	(1,182)		1,962		(3,144)
Common stock dividends	(87,416)			(87,416)
Ending balance (in shares) at Sep. 30, 2016		144,133,304
Ending balance at Sep. 30, 2016	3,378,054		1,718,413	2,106,121	(439,306)	(7,174)
Beginning balance at Jun. 30, 2016						(1,712)
Increase (Decrease) in Stockholders' Equity
Net income	110,143
Other comprehensive loss	(5,462)					(5,462)
Tax benefit from stock compensation plans, net	14
Ending balance (in shares) at Sep. 30, 2016		144,133,304
Ending balance at Sep. 30, 2016	$ 3,378,054		$ 1,718,413	$ 2,106,121	$ (439,306)	$ (7,174)