Business Segments (Details) - USD ($) $ in Millions	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
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,747.4				$ 786.5				$ 1,747.4	$ 786.5
Depreciation and amortization:
Depreciation and amortization									457.8	245.5	$ 230.1
Depreciation and Amortization of Intangible Assets									434.3	234.3	222.5
Net revenues:
Net sales	2,244.8	$ 2,269.9	$ 2,218.7	$ 1,772.3	1,512.7	$ 1,551.8	$ 1,516.4	$ 1,430.7	8,505.7	6,011.6	5,808.3
Reimbursement Revenue									174.4	0.0	0.0
Revenues									8,680.1	6,011.6	5,808.3
Operating Income (Loss)									1,002.9	910.4	990.9
Nonoperating Income (Expense)									(270.8)	(83.7)	(75.3)
Total pre-tax income									732.1	826.7	915.6
Provision for income taxes									294.1	314.1	340.2
Net earnings									438.0	512.6	575.4
Net Income (Loss) Attributable to Noncontrolling Interest									(1.1)	(1.4)	(1.6)
Net earnings attributable to Laboratory Corporation of America Holdings	114.2	$ 152.8	$ 168.4	$ 1.5	$ 119.6	$ 137.2	$ 141.3	$ 113.1	436.9	511.2	573.8
LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	775.7								775.7
Depreciation and amortization:
Depreciation and amortization									245.8	184.8	176.3
Net revenues:
Net sales									6,199.3	5,838.0	5,669.4
Operating Income (Loss)									1,061.4	982.3	1,061.8
Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	971.7								971.7
Depreciation and amortization:
Depreciation and amortization									184.4	5.3	4.1
Net revenues:
Net sales									2,306.4	173.6	138.9
Reimbursement Revenue									174.4	0.0	0.0
Operating Income (Loss)									71.9	40.7	37.9
Corporate Segment [Member]
Depreciation and amortization:
Depreciation and amortization									4.1	44.2	42.1
Net revenues:
Operating Income (Loss)									(130.4)	$ (112.6)	$ (108.8)
UNITED STATES
Segment Reporting Information [Line Items]
Property, plant and equipment, net	1,411.9								1,411.9
Net revenues:
Net sales									7,003.3
UNITED STATES | LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	724.1								724.1
Net revenues:
Net sales									5,847.3
UNITED STATES | Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	687.8								687.8
Net revenues:
Net sales									1,156.0
CANADA
Segment Reporting Information [Line Items]
Property, plant and equipment, net	45.1								45.1
Net revenues:
Net sales									290.4
CANADA | LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	45.1								45.1
Net revenues:
Net sales									290.4
CANADA | Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	0.0								0.0
Net revenues:
Net sales									0.0
UNITED KINGDOM
Segment Reporting Information [Line Items]
Property, plant and equipment, net	136.2								136.2
Net revenues:
Net sales									281.7
UNITED KINGDOM | LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	3.2								3.2
Net revenues:
Net sales									46.2
UNITED KINGDOM | Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	133.0								133.0
Net revenues:
Net sales									235.5
SWITZERLAND
Segment Reporting Information [Line Items]
Property, plant and equipment, net	86.4								86.4
Net revenues:
Net sales									359.7
SWITZERLAND | LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	0.0								0.0
Net revenues:
Net sales									0.0
SWITZERLAND | Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	86.4								86.4
Net revenues:
Net sales									359.7
Other countries [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	67.8								67.8
Net revenues:
Net sales									570.6
Other countries [Member] | LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	3.3								3.3
Net revenues:
Net sales									15.4
Other countries [Member] | Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 64.5								64.5
Net revenues:
Net sales									$ 555.2