Share-Based Compensation (Compensation Expense Of The Nonvested Shares Outstanding) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Remaining 2013	$ 5.0
2014	4.5
2015	2.5
2016	0.4
Total	$ 12.4

Compensation Expense Of Nonvested Shares Outstanding Remainder of Fiscal Year

No definition available.

Name:	swc_CompensationExpenseOfNonvestedSharesOutstandingRemainderOfFiscalYear
Namespace Prefix:	swc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant