EARNINGS PER SHARE Stock Split (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share, Basic and Diluted, by Common Class
Numerator for basic and diluted earnings per common share										$ 240,776	$ 242,215	$ 231,408
Denominator:
Basic earnings per common share — weighted average common shares outstanding										153,670,087	155,363,848	155,736,384
Incremental shares for stock options, ESPP shares and performance shares — weighted average assumed conversion										1,031,034	1,453,804	1,288,620
Diluted earnings per common share — adjusted weighted average shares and assumed conversion										154,701,121	156,817,652	157,025,004
Per common share net income:
Basic earnings per common share		$ 0.25	$ 0.42	$ 0.47	$ 0.43	$ 0.30	$ 0.47	$ 0.34	$ 0.44	$ 1.57	$ 1.56	$ 1.49
Diluted		$ 0.24	$ 0.42	$ 0.46	$ 0.43	$ 0.30	$ 0.47	$ 0.34	$ 0.43	$ 1.56	$ 1.54	$ 1.47
Percentage allocated to common shares:
Weighted average restricted shares (participating securities)										1,102,051	1,277,128	1,472,967
Denominator for percentage allocated to common shares - total weighted-average shares outstanding										154,772,138	156,640,976	157,209,351
Percentage allocated to common shares	[1]									99.30%	99.20%	99.10%
Outstanding stock options and ESPP shares		4,096,910				4,603,292				4,096,910	4,603,292	5,169,828
Anti-dilutive stock options and ESPP shares										1,056,250	550,178	912,570
Reported
Earnings Per Share, Basic and Diluted, by Common Class
Numerator for basic and diluted earnings per common share												$ 231,408
Denominator:
Basic earnings per common share — weighted average common shares outstanding												51,912,128
Incremental shares for stock options, ESPP shares and performance shares — weighted average assumed conversion												429,540
Diluted earnings per common share — adjusted weighted average shares and assumed conversion												52,341,668
Per common share net income:
Basic earnings per common share												$ 4.46
Diluted												$ 4.42
Percentage allocated to common shares:
Weighted average restricted shares (participating securities)												490,989
Denominator for percentage allocated to common shares - total weighted-average shares outstanding												52,403,117
Percentage allocated to common shares												99.10%
Outstanding stock options and ESPP shares												1,723,276
Anti-dilutive stock options and ESPP shares												304,190
Adjustment
Earnings Per Share, Basic and Diluted, by Common Class
Numerator for basic and diluted earnings per common share												$ 0
Denominator:
Basic earnings per common share — weighted average common shares outstanding												103,824,256
Incremental shares for stock options, ESPP shares and performance shares — weighted average assumed conversion												859,080
Diluted earnings per common share — adjusted weighted average shares and assumed conversion												104,683,336
Per common share net income:
Basic earnings per common share												$ (2.97)
Diluted												$ (2.95)
Percentage allocated to common shares:
Weighted average restricted shares (participating securities)												981,978
Denominator for percentage allocated to common shares - total weighted-average shares outstanding												104,806,234
Percentage allocated to common shares												0.00%
Outstanding stock options and ESPP shares												3,446,552
Anti-dilutive stock options and ESPP shares												608,380

[1] Weighted-average common shares outstanding153,670,087 155,363,848 155,736,384Weighted-average restricted shares and deferred stock units (participating securities)1,102,051 1,277,128 1,472,967 Total154,772,138 156,640,976 157,209,351 Percentage allocated to common shares99.3% 99.2% 99.1%