Statement of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Accrued capital expenditures	$ 35.1	$ 8.1	$ 16.1	$ 8.6
Facility lease obligation recognized during the period	$ 50.6	$ 4.7

Carrying value as of the balance sheet date of obligations incurred and payable for purchases of fixed assets. Included in accounts payable and accrued expenses.

No definition available.

Name:	regn_AccruedCapitalExpenditures
Namespace Prefix:	regn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant