Accumulated Other Comprehensive Income (Loss) (Summary Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	$ 1,131,424	$ 1,132,487	$ 1,157,778	$ 1,176,572	$ 1,132,487	$ 1,176,572
Unrealized gain (loss) on available for sale debt securities of the Joint Venture, net of taxes	1,173				1,173
Foreign currency translation adjustment of the Joint Venture	(1,583)	(226)	(566)	2,593	(1,809)	2,027
Balance	1,886,107	1,131,424	1,142,480	1,157,778	1,886,107	1,142,480
Available For Sale Debtr Security [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Unrealized gain (loss) on available for sale debt securities of the Joint Venture, net of taxes	1,173
Balance	1,173				1,173
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(1,339)	(1,565)	(1,325)	1,268	(1,565)	1,268
Foreign currency translation adjustment of the Joint Venture	(1,583)	(226)	(566)	2,593
Balance	244	(1,339)	(759)	(1,325)	244	(759)
Cash Flow Hedge [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(6,700)	(1,691)	2,540	1,268	(1,691)	1,268
Change associated with current period hedging	(1,509)	(5,117)	1,866	1,206
Reclassification into earnings	199	(314)	(388)	(424)
Balance	(8,010)	(6,700)	4,018	2,540	(8,010)	4,018
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(8,039)	(3,256)	1,215	2,536	(3,256)	2,536
Unrealized gain (loss) on available for sale debt securities of the Joint Venture, net of taxes	1,173
Foreign currency translation adjustment of the Joint Venture	(1,583)	(226)	(566)	2,593
Change associated with current period hedging	(1,509)	(5,117)	1,866	1,206
Reclassification into earnings	199	(314)	(388)	(424)
Balance	$ (6,593)	$ (8,039)	$ 3,259	$ 1,215	$ (6,593)	$ 3,259
ASU 2017-12 [Member] | Cash Flow Hedge [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Cumulative effect of accounting change of the Joint Venture								$ 490
ASU 2017-12 [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Cumulative effect of accounting change of the Joint Venture								$ 490
ASU 2018-02 [Member] | Cash Flow Hedge [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Cumulative effect of accounting change of the Joint Venture							$ 422
ASU 2018-02 [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Cumulative effect of accounting change of the Joint Venture							$ 422