Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
NVLS I, LLC Aircraft Lease Expense [Member]
Related Party Transaction [Line Items]
Related party transactions	$ 1.0	$ 1.0	$ 0.8
Aggregate Compensation For Family Members Of Executive Officers [Member]
Related Party Transaction [Line Items]
Related party transactions	0.5	0.6	0.5
Total Legal Expenses For Services Performed By Related Party Law Firm [Member]
Related Party Transaction [Line Items]
Related party transactions	$ 1.2	$ 1.8

Expenses recognized during the period resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 57

-Paragraph 2

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Name:	us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration