Treasury Stock and Subsequent Event - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended			0 Months Ended			6 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013	Nov. 04, 2013 Subsequent Event [Member]	Aug. 31, 2013 Minimum [Member]	Aug. 31, 2013 Maximum [Member]	Sep. 30, 2013 Common Class A [Member]
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to repurchase							2,000,000	34,000,000
Treasury stock, value	$ (321,053,000)		$ (321,053,000)		$ (301,301,000)
Treasury stock, shares	31,974,629		31,974,629		31,317,014
Common stock equals to percentage of outstanding common stock			0.60%
Average price						$ 37.75			$ 10.04
Common stock repurchased shares	372,076		657,615
Purchase of treasury stock	12,400,000		19,752,000	6,937,000
Common stock outstanding	20,984,675		20,984,675		21,520,248
Common stock repurchased shares						72,387
Purchase of treasury stock						$ 2,733,000
Stock split ratio		2
Stock dividend percentage		100.00%
Stock dividend distribution date		Jun. 26, 2013
Stock dividend recording date		Jun. 12, 2013