Common Stock and Treasury Stock (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Mar. 31, 2017
Class A Common Stock [Member]
Common Stock [Line Items]
Balance, shares	6,603
Conversion of shares	12
Issuance of restricted stock	23
Balance, shares	6,638
Balance, shares	6,603	6,638
Class B Common Stock [Member]
Common Stock [Line Items]
Balance, shares	865
Conversion of shares	(12)
Issuance of restricted stock	25
Balance, shares	878
Balance, shares	865	878