v2.4.0.8

Stockholders' Equity (Details 2) (Class A common stock, USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013
Class A common stock |
Common Stock Repurchase Program |
Amount of shares authorized for repurchase | $ 500.0

X
- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of a stock repurchase plan authorized by an entity's Board of Directors. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
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Period Type: | duration