Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Aug. 01, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	SEACOR HOLDINGS INC /NEW/
Entity Central Index Key	0000859598
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		17,730,315
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes