Multiemployer Pension Plans (Details) (AMOPP [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012
AMOPP [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement benefit plans, withdrawal liability	$ 39.3

Pension And Other Postretirement Benefit Plans, Withdrawal Liability

No definition available.

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Namespace Prefix:	ckh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant