Common Stock (Details) (Executive Employees [Member], Class A Nonvoting Common Stock [Member])	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Executive Employees [Member] \| Class A Nonvoting Common Stock [Member]
Common Stock [Line Items]
Stocks granted	125,209	217,890

Number of share instruments newly issued under a share-based compensation plan.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration