Subsequent Events	12 Months Ended
Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On March 21, 2018, the Company increased the authorized number of Class A common stock issuable under its 2007 Long-Term Incentive Plan by 6.0 million shares.

The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 855
-URI http://asc.fasb.org/topic&trid=2122774

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