Fair Value Measurements (Details Textual) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013
Fair Value Measurements (Textual) [Abstract]
Assets measured	$ 2,069,148,000	$ 1,668,260,000
Liquidating distributions payable	25,046,000	16,555,000
Transfers between fair value amount	0	0
Level 3 [Member]
Fair Value Measurements (Textual) [Abstract]
Assets measured	0	0
Liquidating distributions payable	$ 0	$ 0