Corporate Debt (Narrative - Convertible Senior Subordinated Notes) (Details) (USD $)	3 Months Ended		9 Months Ended					9 Months Ended						0 Months Ended										3 Months Ended				9 Months Ended				3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2012	Dec. 31, 2012 Term Loan [Member]	Mar. 31, 2012 Term Loan [Member]	Dec. 31, 2012 Convertible Senior Subordinated Notes [Member]	Dec. 31, 2011 Convertible Senior Subordinated Notes [Member]	Mar. 31, 2012 Convertible Senior Subordinated Notes [Member]	Dec. 31, 2012 Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Mar. 31, 2012 Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Oct. 31, 2004 Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Jul. 17, 2012 Convertible Senior Subordinated Notes [Member] February 2005 Notes [Member]	Dec. 31, 2012 Convertible Senior Subordinated Notes [Member] February 2005 Notes [Member]	Mar. 31, 2012 Convertible Senior Subordinated Notes [Member] February 2005 Notes [Member]	Dec. 31, 2012 Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Mar. 31, 2012 Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Apr. 30, 2009 Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Dec. 31, 2012 Convertible Senior Subordinated Notes [Member] January 2012 Notes [Member]	Mar. 31, 2012 Convertible Senior Subordinated Notes [Member] January 2012 Notes [Member]	Jan. 31, 2012 Convertible Senior Subordinated Notes [Member] January 2012 Notes [Member]	Dec. 31, 2012 February 2005 Notes [Member] Convertible Senior Subordinated Notes [Member]	Dec. 31, 2012 Issuer [Member] Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Dec. 31, 2012 Issuer [Member] On or After March 15, 2015 [Member] Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Dec. 31, 2012 Holder [Member] Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Dec. 31, 2012 Holder [Member] On October 15, 2014, October 15, 2019 or Upon a Change in Control [Member] Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Dec. 31, 2012 Common Shares [Member] Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Dec. 31, 2012 Common Shares [Member] Convertible Senior Subordinated Notes [Member] February 2005 Notes [Member]	Dec. 31, 2012 Common Shares [Member] Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Jan. 11, 2012 Common Shares [Member] Convertible Senior Subordinated Notes [Member] January 2012 Notes [Member]	Dec. 31, 2012 Common Shares [Member] Minimum [Member] Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Dec. 31, 2012 Common Shares [Member] Minimum [Member] Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Dec. 31, 2012 Common Shares [Member] Maximum [Member] Convertible Senior Subordinated Notes [Member] October 2004 Notes [Member]	Dec. 31, 2012 Common Shares [Member] Maximum [Member] Convertible Senior Subordinated Notes [Member] April 2009 Notes [Member]	Dec. 31, 2012 October 2004 Notes [Member]	Dec. 31, 2012 January 2012 Notes [Member]	Dec. 31, 2012 April 2009 Notes [Member]
Principal amount of notes													$ 150,000,000						$ 66,600,000			$ 45,000,000
Coupon rate											2.9375%				3.625%		3.625%			4.00%			3.625%													2.9375%	4.00%	3.625%
Amount of debt redeemed														23,500,000
Debt instrument, amount redeemed for cash														7,700,000
Equity component											50,100,000								16,200,000			10,100,000
Loss on extinguishment of debt	(14,652,000)	0	(23,811,000)	(967,000)				(23,811,000)	(967,000)
Principal amount of debt outstanding	993,396,000		993,396,000			0	484,664,000	110,922,000		135,393,000	348,000	348,000			0	23,464,000	65,574,000	66,581,000		45,000,000	45,000,000
Carrying value of debt outstanding	964,508,000		964,508,000		1,117,050,000	0	477,514,000	85,958,000		104,498,000	348,000	348,000			0	23,464,000	49,134,000	45,462,000		36,476,000	35,224,000
Debt instrument redemption price percentage														100.00%										100.00%	100.00%	100.00%	100.00%
Conversion rate of number of common shares of the company per $1,000 principal amount of new notes																												86.9565	70.0133	121.2121
Debt instrument, denomination amount								$ 1,000
Conversion price per share											$ 11.50				$ 14.28		$ 8.25			$ 10.50								$ 11.50	$ 14.28	$ 8.25	$ 10.50					$ 11.50	$ 10.50	$ 8.25
Applicable price range for make-whole premium																																$ 8.79	$ 5.36	$ 50.00	$ 50.00