CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Millions, unless otherwise specified	Total	Common stock	Additional Paid-in Capital	Retained Earnings	Treasury stock	Accumulated Other Comprehensive Income (Loss)
BALANCE at Dec. 31, 2008	$ 1,688.3	$ 12.8	$ 237.4	$ 2,384.6	$ (929.8)	$ (16.7)
Comprehensive earnings:
Net earnings attributable to Laboratory Corporation of America Holdings	543.3	0	0	543.3	0	0
Other comprehensive earnings:
Foreign currency translation adjustments	93.3	0	0	0	0	93.3
Interest rate swap adjustments	2.9	0	0	0	0	2.9
Net benefit plan adjustments	31.5	0	0	0	0	31.5
Tax effect of other comprehensive earnings adjustments	(49.5)	0	0	0	0	(49.5)
Comprehensive earnings	621.5
Issuance of common stock under employee stock plans	24.8	0	24.8	0	0	0
Surrender of restricted stock awards and performance shares	(2.7)	0	0	0	(2.7)	0
Conversion of zero-coupon convertible debt	11.4	0.1	11.3	0	0	0
Stock compensation	36.4	0	36.4	0	0	0
Income tax benefit from stock options exercised	(0.1)	0	(0.1)	0	0	0
Purchase of common stock	(273.5)	(0.4)	(273.1)	0	0	0
BALANCE at Dec. 31, 2009	2,106.1	12.5	36.7	2,927.9	(932.5)	61.5
Comprehensive earnings:
Net earnings attributable to Laboratory Corporation of America Holdings	558.2	0	0	558.2	0	0
Other comprehensive earnings:
Foreign currency translation adjustments	41.3	0	0	0	0	41.3
Interest rate swap adjustments	8.2	0	0	0	0	8.2
Net benefit plan adjustments	(8.3)	0	0	0	0	(8.3)
Tax effect of other comprehensive earnings adjustments	(14.2)	0	0	0	0	(14.2)
Comprehensive earnings	585.2
Issuance of common stock under employee stock plans	83.4	0.2	83.2	0	0	0
Surrender of restricted stock awards and performance shares	(2.4)	0	0	0	(2.4)	0
Conversion of zero-coupon convertible debt	1.1	0	1.1	0	0	0
Stock compensation	40.0	0	40.0	0	0	0
Purchase of noncontrolling interest	(17.2)	0	(17.2)	0	0	0
Income tax benefit from stock options exercised	7.6	0	7.6	0	0	0
Purchase of common stock	(337.5)	(0.5)	(97.5)	(239.5)	0	0
BALANCE at Dec. 31, 2010	2,466.3	12.2	53.9	3,246.6	(934.9)	88.5
Comprehensive earnings:
Net earnings attributable to Laboratory Corporation of America Holdings	519.7	0	0	519.7	0	0
Other comprehensive earnings:
Foreign currency translation adjustments	(13.2)	0	0	0	0	(13.2)
Interest rate swap adjustments	2.4	0	0	0	0	2.4
Net benefit plan adjustments	(57.5)	0	0	0	0	(57.5)
Tax effect of other comprehensive earnings adjustments	25.3	0	0	0	0	25.3
Comprehensive earnings	476.7
Issuance of common stock under employee stock plans	118.5	0.1	118.4	0	0	0
Surrender of restricted stock awards and performance shares	(6.0)	0	0	0	(6.0)	0
Conversion of zero-coupon convertible debt	36.2	0.1	36.1	0	0	0
Stock compensation	48.9	0	48.9	0	0	0
Purchase of noncontrolling interest	(3.7)	0	(3.7)	0	0	0
Income tax benefit from stock options exercised	10.5	0	10.5	0	0	0
Purchase of common stock	(643.9)	(0.7)	(264.1)	(379.1)	0	0
BALANCE at Dec. 31, 2011	$ 2,503.5	$ 11.7	$ 0	$ 3,387.2	$ (940.9)	$ 45.5