Subsequent Events (Details) (Subsequent event, USD $)	Feb. 18, 2014
Class A common stock
Subsequent events
Quarterly dividend declared (in dollars per share)	$ 0.13
Class B common stock
Subsequent events
Quarterly dividend declared (in dollars per share)	$ 0.13

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 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