STOCKHOLDERS' EQUITY Changes in Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Beginning balance, shares	152,699,077
Beginning balance	$ 1,709,071
NET INCOME	64,237	$ 67,132
Other comprehensive loss, net of tax	$ (2,162)	$ (621)
Ending balance, shares	152,766,017
Ending balance	$ 1,748,814
Parenthetical Disclosures
Dividends declared per common share	$ 0.1875	$ 0.1625
Common Stock
Beginning balance, shares	152,699,077	155,140,967
Beginning balance	$ 829,211	$ 923,191
Repurchase and retirement of common stock, shares	(28,875)	(11,917)
Repurchase and retirement of common stock	$ (1,176)	$ (476)
Stock option exercises, shares	84,006	37,495
Stock option exercises	$ 1,847	$ 665
Shares issued under the employee stock purchase plan, shares	23,276	17,267
Shares issued under the employee stock purchase plan	$ 647	$ 581
Issuance of restricted stock, shares	3,896	27,776
Forfeiture of restricted stock, shares	(11,737)	(13,772)
Forfeiture of performance, shares	(3,626)
Share-based compensation, net of forfeitures	$ 4,933	$ 3,853
Other	$ 51
Ending balance, shares	152,766,017	155,197,816
Ending balance	$ 835,513	$ 927,814
Retained Earnings
Beginning balance	875,595	741,550
NET INCOME	64,237	67,132
Dividends, common stock	(28,634)	(25,220)
Ending balance	911,198	783,462
Accumulated Other Comprehensive Income (Loss)
Beginning balance	4,265	4,816
Other comprehensive loss, net of tax	(2,162)	(621)
Ending balance	2,103	4,195
Total Stockholders' Equity
Beginning balance	1,709,071	1,669,557
NET INCOME	64,237	67,132
Repurchase and retirement of common stock	(1,176)	(476)
Dividends, common stock	(28,634)	(25,220)
Stock option exercises	1,847	665
Shares issued under the employee stock purchase plan	647	581
Share-based compensation, net of forfeitures	4,933	3,853
Other comprehensive loss, net of tax	(2,162)	(621)
Other	51
Ending balance	$ 1,748,814	$ 1,715,471