BUSINESS ACQUISITIONS (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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	Dec. 31, 2012	Feb. 19, 2015	Jan. 30, 2015	Dec. 19, 2014	Nov. 20, 2014	Nov. 01, 2013
Business Acquisition [Line Items]
Stock Issued During Period, Shares, Acquisitions									15.3
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability									$ 1.7	$ 10.4	$ 5.8
Employee Severance Benefits Related Restructuring Reserve Accrual Adjustment											0.4	$ 0.7
Facility Related Restructuring Reserve Accrual Adjustment										1.1	0.7	$ 2.4
Cost of Acquired Entity [Abstract]
Goodwill, net	$ 6,227.7				$ 3,099.4				6,227.7	3,099.4	3,022.8
Payments to Acquire Businesses, Net of Cash Acquired									3,736.0	159.4	159.5
Finite-lived Intangible Assets Acquired									2,176.5
Goodwill, Acquired During Period									3,141.1	81.8
Line of Credit Facility, Maximum Borrowing Capacity	1,000.0								$ 1,000.0						$ 1,000.0
Purchase Price Allocation [Abstract]
Weighted-average useful lives of identifiable intangible assets									26 years 11 months 28 days
Cash payments to acquire laboratory-related assets									$ 255.8	203.5	202.2
Senior Notes, Noncurrent	2,900.0								2,900.0					$ 2,900.0			$ 700.0
Noncontrolling Interest Put [Abstract]
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
Proforma consolidated net revenue										2,209.7
Proforma consolidated net income										167.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	0.0								0.0				$ 780.8
Business Combination, Acquired Receivables, Fair Value	0.0								0.0				334.8
Unbilled Receivables, Current	92.5								92.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory	0.0								0.0				51.9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent	0.0								0.0				34.4
Revenues									8,680.1	6,011.6	5,808.3
Operating Income (Loss)									1,002.9	910.4	990.9
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
Basic Earnings Per Share, Pro Forma									$ 5,040,000	$ 4,220,000
Proforma consolidated diluted earnings per share									$ 5,020,000	$ 4,160,000
Senior notes due 2025 [Member]
Purchase Price Allocation [Abstract]
Debt Instrument, Interest Rate, Stated Percentage														3.60%
Senior Notes, Noncurrent														$ 1,000.0
Laboratories and Related Assets [Member]
Purchase Price Allocation [Abstract]
Cash payments to acquire laboratory-related assets										$ 159.5
Excluding Covance [Member]
Cost of Acquired Entity [Abstract]
Payments to Acquire Businesses, Net of Cash Acquired										$ 128.6
Finite-lived Intangible Assets Acquired									$ 17.4
Goodwill, Acquired During Period									68.4
Covance, Inc. [Member]
Business Acquisition [Line Items]
Legal Fees									75.6
Noncontrolling Interest Put [Abstract]
Change in control and severance payments									26.8
Write off of bridge and other deferred financing costs									15.2
LipoScience [Member]
Business Acquisition [Line Items]
Business Acquisition, Share Price																$ 5.25
Cost of Acquired Entity [Abstract]
Business combination, recognized identifiable intangible assets acquired																$ 27.2
Business combination, recognized identifiable deferred tax liabilities assumed																9.4
Goodwill, net																$ 17.4
Payments to Acquire Businesses, Net of Cash Acquired					67.9
Purchase Price Allocation [Abstract]
Weighted-average useful lives of identifiable intangible assets										19 years 6 months
Acquisitions excluding LipoScience [Member]
Cost of Acquired Entity [Abstract]
Payments to Acquire Businesses, Net of Cash Acquired										$ 91.5
Finite-lived Intangible Assets Acquired										22.0
Goodwill, Acquired During Period										63.4
Covance [Member]
Business Acquisition [Line Items]
Cash on Hand Used for Acquisition													488.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Deferred Revenue													168.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets													7,939.7
Cash paid for acquisition													1,762.5
Non-cash consideration													4,388.2
Total acquisition consideration (cash and non-cash)													$ 6,150.7
Business Acquisition, Share Price													$ 75.76
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Rate				26.86%
Acquisition Financing													$ 3,900,000.0
Business Acquisition, Transaction Costs					166.0					166.0
Post combination acceleration of stock compensation expense									43.2
Employer taxes on accelerated equity									9.4
Purchase Price Allocation [Abstract]
Net Proceeds from Debt														$ 2,870.2
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents													780.8
Business Combination, Acquired Receivables, Fair Value													334.8
Unbilled Receivables, Current													138.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory													51.9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities													280.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable													190.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets													12.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent													34.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent													791.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt													250.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other													108.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities													1,789.0
Revenues									9,033.3	8,711.2
Operating Income (Loss)									1,123.3	907.7
Net earnings attributable to Laboratory Corporation of America Holdings									546.8	423.0
Transaction costs									207.6
Make-whole payment									$ 37.4
Selling, General and Administrative Expenses [Member]
Business Acquisition [Line Items]
Other Special Charges										25.6
Selling, General and Administrative Expenses [Member] | Covance [Member]
Business Acquisition [Line Items]
Business Acquisition, Transaction Costs					113.4					113.4
Interest Expense [Member] | Covance [Member]
Business Acquisition [Line Items]
Business Acquisition, Transaction Costs					$ 52.6					$ 52.6
60-Day Debt Bridge Traunche [Domain]
Cost of Acquired Entity [Abstract]
Bridge Term Credit Facility Agreement, Maximum Borrowing Amount															$ 400.0
Short-term Debt, Terms										P60D
Scenario, Previously Reported [Member] | Covance [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets													7,849.0
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent													730.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other													78.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities													1,698.3
Assets, Total [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									90.7
Goodwill [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									-135.9
Goodwill [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													3,040.2
Goodwill [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													3,176.1
Other Assets [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									-3.2
Other Assets [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets													15.2
Property, Plant and Equipment [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									174
Prepaid Expenses and Other Current Assets [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									86.5
Prepaid Expenses and Other Current Assets [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets													261.4
Accounts Payable [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									0
Accounts Payable [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets													190.8
Accrued Liabilities [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									0
Accrued Liabilities [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets													280.8
Deferred tax liability [Domain] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									61.2
Other Liabilities [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									29.5
Liabilities, Total [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Items									90.7
Off-Market Favorable Lease [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles									$ 5.5
Off-Market Favorable Lease [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													5.5
Off-Market Favorable Lease [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													0.0
Software and Software Development Costs [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles									$ 74.5
Software and Software Development Costs [Member] | Covance [Member]
Purchase Price Allocation [Abstract]
Weighted-average useful lives of identifiable intangible assets									10 years
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													74.5
Software and Software Development Costs [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													0.0
Use Rights [Member]
Cost of Acquired Entity [Abstract]
Finite-lived Intangible Assets Acquired									$ 5.5
Use Rights [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles									$ (4.9)
Use Rights [Member] | Covance [Member]
Purchase Price Allocation [Abstract]
Weighted-average useful lives of identifiable intangible assets									8 years
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													0.0
Use Rights [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													4.9
Trademarks and Trade Names [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles									$ (18.9)
Trademarks and Trade Names [Member] | Covance [Member]
Purchase Price Allocation [Abstract]
Weighted-average useful lives of identifiable intangible assets									15 years
Trade Names [Member]
Cost of Acquired Entity [Abstract]
Finite-lived Intangible Assets Acquired									$ 270.5
Purchase Price Allocation [Abstract]
Weighted-average useful lives of identifiable intangible assets									15 years
Trade Names [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													270.5
Trade Names [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													289.4
Customer Relationships [Member]
Cost of Acquired Entity [Abstract]
Finite-lived Intangible Assets Acquired									$ 1,855.0
Acquired Finite-lived Intangible Assets, Useful Life									28 years
Purchase Price Allocation [Abstract]
Weighted-average useful lives of identifiable intangible assets									29 years 2 months 16 days
Customer Relationships [Member] | Covance, Inc. [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles									$ (86.9)
Customer Relationships [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets													347.9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment													1,018.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													1,830.3
Customer Relationships [Member] | Scenario, Previously Reported [Member] | Covance [Member]
Noncontrolling Interest Put [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment													844.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill													$ 1,917.2