Treasury Stock and Subsequent Event (Details) (USD $)	3 Months Ended	6 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2012	Feb. 29, 2012
Treasury Stock and Subsequent Event (Textual) [Abstract]
Common stock repurchase shares	72,274	158,946
Common stock repurchased value	$ 3,300,000	$ 6,937,000	$ 10,005,000
Common stock equals to percentage of out standing common stock		57.00%
Common stock repurchase price	277,510,000	277,510,000		270,574,000	278,000,000
Common stock, shares outstanding	11,238,777	11,238,777		11,308,773
Common Class A [Member]
Treasury Stock and Subsequent Event (Textual) [Abstract]
Average price per share		$ 18.36
Future Shares [Member]
Treasury Stock and Subsequent Event (Textual) [Abstract]
Common stock repurchase shares		30,628
Common stock repurchased value		$ 1,355,000
Average price per share		$ 44.24
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