Common Stock and Treasury Stock (Details) - shares shares in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Class A Common Stock [Member]
Common Stock [Line Items]
Balance, shares	6,603	6,446
Exercised options		93
Conversion of shares		40
Issuance of restricted stock		26
Forfeiture of restricted stock		(2)
Balance, shares	6,603	6,603
Class B Common Stock [Member]
Common Stock [Line Items]
Balance, shares	865	843
Exercised options		32
Conversion of shares		(40)
Issuance of restricted stock		30
Forfeiture of restricted stock		0
Balance, shares	865	865