EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income (Numerator)
Income available to common shareholders (in dollars)	$ 36,899	$ 45,264	$ 49,802	$ 40,029	$ 34,990	$ 42,127	$ 41,686	$ 43,809	$ 171,994	$ 162,612	$ 183,683
Shares (Denominator)
Income available to common stockholders - Basic (in shares)	65,700	66,092	66,420	66,155	66,249	66,541	66,580	66,196	66,090	66,392	66,553
Income available to common stockholders - Diluted (in shares)	67,853	67,986	68,106	68,296	67,846	68,353	68,758	68,785	68,208	68,395	69,274
Per Share Amount
Income available to common stockholders - Basic (in dollars per share)	$ 0.56	$ 0.68	$ 0.75	$ 0.61	$ 0.53	$ 0.63	$ 0.63	$ 0.66	$ 2.60	$ 2.45	$ 2.76
Income available to common stockholders - Diluted (in dollars per share)	$ 0.54	$ 0.67	$ 0.73	$ 0.59	$ 0.52	$ 0.62	$ 0.61	$ 0.64	$ 2.52	$ 2.38	$ 2.65
Stock options
Shares (Denominator)
Effect of Dilutive Securities (in shares)									2,106	1,990	2,714
Restricted stock
Shares (Denominator)
Effect of Dilutive Securities (in shares)									12	13	7