Treasury Stock and Subsequent Event (Details) (USD $)	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2012	Feb. 29, 2012
Treasury Stock and Subsequent Event (Textual) [Abstract]
Treasury stock, shares	15,039,713		14,953,101
Common stock repurchase shares	86,612
Common stock repurchased value	$ 3,673,000	$ 3,673,000
Common stock equals to percentage of out standing common stock	57.00%
Common stock repurchase price	274,246,000		270,574,000	274,000,000
Common stock, shares outstanding	11,274,291		11,308,773
Common Class A [Member]
Treasury Stock and Subsequent Event (Textual) [Abstract]
Average price per share	$ 18.23
Future Shares [Member]
Treasury Stock and Subsequent Event (Textual) [Abstract]
Treasury stock, shares	9,818
Common stock repurchase price	$ 445,000
Average price per share	$ 45.40
Maximum [Member]
Treasury Stock and Subsequent Event (Textual) [Abstract]
Number of shares authorized to repurchase				16,000,000
Minimum [Member]
Treasury Stock and Subsequent Event (Textual) [Abstract]
Number of shares authorized to repurchase				1,000,000