Repurchase of Common Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	May 22, 2012	Jul. 28, 2012	Mar. 28, 2012
Repurchase of Common Stock (Textual) [Abstract]
Purchase cost	102.0
Additional shares of Class A common stock	285,009
Class A common stock [Member]
Repurchase of Common Stock (Textual) [Abstract]
Self-tender offer to repurchase, maximum			1,950,000
Purchase of common shares	2,235,009
Percentage of additional shares of Class A stock		2.00%
Class B common stock [Member]
Repurchase of Common Stock (Textual) [Abstract]
Self-tender offer to repurchase, maximum			500,000
Purchase of common shares	266,136
Common stock [Member]
Repurchase of Common Stock (Textual) [Abstract]
Price per share of shares purchased under self-tender offer			40.80