Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Repurchase of Class A Common Stock, shares			1,356,861
Issuance of treasury shares upon exercise of stock options, purchases under stock purchase plan and grants of restricted stock awards, shares	646,395	1,370,705	963,750
Shares Paid for Tax Withholding for Share Based Compensation	138,881	65,914	165,610
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	250,000
Investment Warrants, Exercise Price	$ 89.34