Common Stock and Treasury Stock (Details Textual) - Class A Common Stock [Member] $ in Millions	Jun. 30, 2015 USD ($)
Common Stock [Line Items]
Share repurchase program, authorized amount	$ 75.8
Stock repurchase program, remaining authorization amount	$ 28.8

Amount remaining of a stock repurchase plan authorized.

No definition available.

Name:	us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant