Corporate Debt (Narrative - Senior Secured Second-Priority Notes) (Details) (USD $)	12 Months Ended						1 Months Ended		12 Months Ended	1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010	Mar. 31, 2012 Senior Secured Second-Priority Notes [Member]	Mar. 31, 2011 Senior Secured Second-Priority Notes [Member]	Mar. 31, 2010 Senior Secured Second-Priority Notes [Member]	Oct. 31, 2009 Senior Secured Second-Priority Notes [Member] October 2009 Senior Notes [Member]	May 31, 2011 Senior Secured Second-Priority Notes [Member] May 2011 Senior Notes [Member]	Mar. 31, 2012 Senior Secured Second-Priority Notes [Member] May 2011 and October 2009 Senior Notes [Member]	Aug. 31, 2011 August 2011 Debt Repurchase [Member] Senior Secured Second-Priority Notes [Member] May 2011 and October 2009 Senior Notes [Member]	Sep. 30, 2011 August 2011 Debt Repurchase [Member] Senior Secured Second-Priority Notes [Member] May 2011 and October 2009 Senior Notes [Member]
Debt Instrument [Line Items]
Principal amount of notes							$ 236,000,000	$ 200,000,000			$ 10,000,000
Senior notes repurchased, amount paid										9,900,000
Principal amount of notes repurchased	125,000									10,000,000
Carrying value of notes extinguished										9,900,000
Loss on extinguishment of debt	(967,000)	(14,505,000)	5,675,000	(967,000)	(14,505,000)	5,675,000					400,000
Write-off of deferred debt financing costs											500,000
Debt instrument, initial issuance price							95.222%	102.219%
Debt instrument, original issue premium (discount)							4.778%	(2.219%)
Initial issuance price											99.00%
Gross proceeds from issuance of debt								204,400,000			10,200,000
Proceeds from debt, net of fees and expenses	476,150,000	0	0	476,150,000				192,400,000
Consent solicitation fee								$ 5,600,000
Remaining amortization period									4 years 7 months
Coupon rate									10.25%