Treasury Stock and Subsequent Event (Details) (USD $)	3 Months Ended			3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013	Jul. 24, 2013 Future Shares [Member]	Jun. 30, 2013 Future Shares [Member]	Jun. 30, 2013 Common Class A [Member]	Feb. 29, 2012 Maximum [Member]	Feb. 29, 2012 Minimum [Member]
Treasury Stock and Subsequent Event (Textual) [Abstract]
Number of shares authorized to repurchase							32,000,000	2,000,000
Treasury Stock (31,317,014 shares at March 31, 2013 and 31,602,553 shares at June 30, 2013)	$ (308,609,000)		$ (301,301,000)
Treasury stock, shares	31,602,553		31,317,014
Common stock equals to percentage of outstanding common stock	60.00%
Common stock outstanding	21,298,885		21,520,248
Shares repurchased					125,293
Purchase of treasury stock	$ (7,308,000)	$ (3,673,000)		$ (3,882,000)
Stock split ratio	2
Stock dividend percentage	100.00%
Stock dividend distribution date	Jun. 26, 2013
Stock dividend recording date	Jun. 12, 2013
Average price				$ 30.98	$ 30.98	$ 9.77
Common stock repurchased shares	285,539			125,293