Subsequent Events (Details) (USD $) In Millions, except Per Share data	1 Months Ended
Oct. 31, 2011
Subsequent events
Charge recorded to freeze defined benefit pension plan	$ 1.4
Class A \| Dividend Declared
Subsequent events
Quarterly dividend declared (in dollars per share)	$ 0.11
Class B \| Dividend Declared
Subsequent events
Quarterly dividend declared (in dollars per share)	$ 0.11

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 32

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

Name:	us-gaap_DividendsPayableAmountPerShare
Namespace Prefix:	us-gaap
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant