Derivative Instruments And Hedging Strategies (Narrative) (Details) In Millions, unless otherwise specified	Jun. 30, 2013 Not Designated as Hedging Instrument [Member] USD ($)	Jun. 30, 2013 SEACOR Holdings Inc. [Member] Not Designated as Hedging Instrument [Member]	Jun. 30, 2013 Offshore Marine Services Joint Ventures [Member] USD ($)	Jun. 30, 2013 Offshore Marine Services Joint Ventures [Member] Cash Flow Hedging [Member]	Jun. 30, 2013 Inland River Joint Venture [Member] USD ($)	Jun. 30, 2013 Inland River Joint Venture [Member] Cash Flow Hedging [Member]	Jun. 30, 2013 Shipping Services [Member] USD ($)	Jun. 30, 2013 Shipping Services [Member] Cash Flow Hedging [Member]	Jun. 30, 2013 Dynamic Offshore Drilling Ltd [Member]	Jun. 30, 2013 Not Designated as Hedging Instrument [Member] Interest Rate Swap Agreements [Member] USD ($)	Jun. 30, 2013 Not Designated as Hedging Instrument [Member] Windcat Acquisition [Member] Interest Rate Swap Agreements [Member] USD ($)	Jun. 30, 2013 Not Designated as Hedging Instrument [Member] Windcat Acquisition [Member] Interest Rate Swap Agreements [Member] EUR (€)	Jun. 30, 2013 Not Designated as Hedging Instrument [Member] Dynamic Offshore Drilling Ltd [Member] Interest Rate Swap Agreements [Member] USD ($)
Derivative [Line Items]
Fixed interest rate range, minimum		2.25%				1.53%
Fixed interest rate range, maximum		3.05%				4.16%
Derivative, Notional Amount	$ 13.1		$ 17.5		$ 38.8		$ 38.4			$ 221.1	$ 14.4	€ 10.9	$ 108.0
Fixed interest rate				1.48%				2.79%	1.30%