EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Numerator for basic and diluted earnings per share:
Income from continuing operations									$ 129,674	$ 127,252	$ 127,721
Income from discontinued operations									0	0	2,794
Net income	$ 61,874	$ 12,359	$ 23,426	$ 32,015	$ 38,233	$ 37,133	$ 29,156	$ 22,730	$ 129,674	$ 127,252	$ 130,515
Denominator:
Basic shares outstanding (in shares)									53,884	52,961	52,622
Dilutive effect of equity-based compensation awards (in shares)									195	363	310
Dilutive shares outstanding (in shares)									54,079	53,324	52,932
Basic earnings per share:
Income from continuing operations (in dollars per share)									$ 2.41	$ 2.40	$ 2.43
Income from discontinued operations, net of tax (in dollars per share)									$ 0.00	$ 0.00	$ 0.05
Net income (in dollars per share)	$ 1.11	$ 0.23	$ 0.44	$ 0.6	$ 0.72	$ 0.70	$ 0.55	$ 0.43	$ 2.41	$ 2.40	$ 2.48
Diluted earnings per share:
Income from continuing operations (in dollars per share)									$ 2.40	$ 2.39	$ 2.42
Income from discontinued operations, net of tax (in dollars per share)									$ 0.00	$ 0.00	$ 0.05
Net income (in dollars per share)	$ 1.11	$ 0.23	$ 0.44	$ 0.6	$ 0.72	$ 0.70	$ 0.55	$ 0.43	$ 2.40	$ 2.39	$ 2.47