EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
EARNINGS PER SHARE
Authorized common stock (in shares)	199,000,000		199,000,000		199,000,000
Common stock par value (in dollars per share)	$ 0.01		$ 0.01		$ 0.01
Diluted
Income available to common shareholders (in dollars)	$ 51,289	$ 46,695	$ 95,766	$ 85,717
Shares of common stock (in shares)	66,939,000	67,630,000	66,933,000	67,603,000
Total average equivalent shares (in shares)	69,438,000	69,682,000	69,902,000	70,070,000
Net income per share, diluted (in dollars per share)	$ 0.74	$ 0.67	$ 1.37	$ 1.22
Basic
Income available to common shareholders (in dollars)	$ 51,289	$ 46,695	$ 95,766	$ 85,717
Shares of common stock (in shares)	66,939,000	67,630,000	66,933,000	67,603,000
Net income per share, basic (in dollars per share)	$ 0.77	$ 0.69	$ 1.43	$ 1.27
Stock options
Diluted
Effect of dilutive stock based compensation (in shares)	2,495,000	2,032,000	2,963,000	2,451,000
Restricted stock units
Diluted
Effect of dilutive stock based compensation (in shares)	4,000	20,000	6,000	16,000