Derivatives and Hedging Derivative Instruments and Hedging Activities Disclosure (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Mar. 31, 2015
Other Assets [Member]
Derivative
Amount Net for Fair Value of Derivative Assets and (Liabilities)		$ 9,991	$ 6,042
Other Liabilities [Member]
Derivative
Amount Net for Fair Value of Derivative Assets and (Liabilities)		14,562	$ 8,665
Foreign Exchange Forward [Member]
Derivative
Derivative, Notional Amount		364,777
Forward Contracts [Member]
Derivative
Derivative, Notional Amount		114,228
RARE Infrastructure, Ltd [Member] | Foreign Exchange Forward [Member]
Derivative
Derivative, Notional Amount	[1]	$ 218,022

[1] Relates to a currency forward executed in August 2015 in connection with the October 2015 acquisition of RARE Infrastructure.