Loans Receivable, Net - Loans Receivable Based On Our Internal Risk Ratings, Separated By Year Of Origination (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Loans receivable	$ 16,339,403		$ 16,164,801
CECL reserve	(178,050)	$ (112,694)	0
Loans receivable, net	16,161,353		16,164,801
Loans Receivable [Member]
Financing receivable, originated in current fiscal year	769,772
Financing receivable, originated in fiscal year before latest fiscal year				$ 5,806,325
Financing receivable, originated two years before latest fiscal year					$ 6,558,869
Financing receivable, originated three years before latest fiscal year						$ 2,070,173
Financing receivable, originated four years before latest fiscal year							$ 545,655
Financing receivable, originated five or more years before latest fiscal year	588,609
Loans receivable	16,339,403
Loans receivable, net	16,161,353		16,164,801
U.S. Loans [Member]
Financing receivable, originated in current fiscal year	673,138
Financing receivable, originated in fiscal year before latest fiscal year				2,856,496
Financing receivable, originated two years before latest fiscal year					4,575,945
Financing receivable, originated three years before latest fiscal year						1,982,951
Financing receivable, originated four years before latest fiscal year							441,775
Financing receivable, originated five or more years before latest fiscal year	452,164
Loans receivable	10,982,469
Non-U.S. Loans [Member]
Financing receivable, originated in current fiscal year	96,634
Financing receivable, originated in fiscal year before latest fiscal year				2,655,337
Financing receivable, originated two years before latest fiscal year					547,870
Financing receivable, originated three years before latest fiscal year						87,222
Financing receivable, originated four years before latest fiscal year							103,880
Loans receivable	3,490,943
Unique Loans [Member]
Financing receivable, originated in fiscal year before latest fiscal year				294,492
Financing receivable, originated two years before latest fiscal year					1,155,180
Financing receivable, originated five or more years before latest fiscal year	83,658
Loans receivable	1,533,330
CECL reserve	(27,240)	(26,008)	0
Impaired Loans [Member]
Financing receivable, originated two years before latest fiscal year					279,874
Financing receivable, originated five or more years before latest fiscal year	52,787
Loans receivable	332,661
CECL reserve	(69,661)	$ 0	0
Risk Rating One [Member]
Loans receivable	403,025		376,379
Risk Rating One [Member] | Loans Receivable [Member]
Financing receivable, originated in current fiscal year	20,362
Financing receivable, originated in fiscal year before latest fiscal year				199,351
Financing receivable, originated two years before latest fiscal year					117,180
Financing receivable, originated three years before latest fiscal year						43,979
Financing receivable, originated four years before latest fiscal year							22,153
Loans receivable	403,025
Risk Rating One [Member] | U.S. Loans [Member]
Financing receivable, originated in current fiscal year	20,362
Financing receivable, originated in fiscal year before latest fiscal year				199,351
Financing receivable, originated three years before latest fiscal year						43,979
Financing receivable, originated four years before latest fiscal year							22,153
Loans receivable	285,845
Risk Rating One [Member] | Non-U.S. Loans [Member]
Financing receivable, originated two years before latest fiscal year					117,180
Loans receivable	117,180
Risk Rating Two [Member]
Loans receivable	3,143,641		3,481,123
Risk Rating Two [Member] | Loans Receivable [Member]
Financing receivable, originated in fiscal year before latest fiscal year				86,727
Financing receivable, originated two years before latest fiscal year					1,907,488
Financing receivable, originated three years before latest fiscal year						846,013
Financing receivable, originated four years before latest fiscal year							79,947
Financing receivable, originated five or more years before latest fiscal year	223,466
Loans receivable	3,143,641
Risk Rating Two [Member] | U.S. Loans [Member]
Financing receivable, originated in fiscal year before latest fiscal year				86,727
Financing receivable, originated two years before latest fiscal year					1,907,488
Financing receivable, originated three years before latest fiscal year						758,791
Financing receivable, originated four years before latest fiscal year							79,947
Financing receivable, originated five or more years before latest fiscal year	223,466
Loans receivable	3,056,419
Risk Rating Two [Member] | Non-U.S. Loans [Member]
Financing receivable, originated three years before latest fiscal year						87,222
Loans receivable	87,222
Risk Rating Three [Member]
Loans receivable	9,509,007		12,137,963
Risk Rating Three [Member] | Loans Receivable [Member]
Financing receivable, originated in current fiscal year	683,550
Financing receivable, originated in fiscal year before latest fiscal year				4,828,050
Financing receivable, originated two years before latest fiscal year					2,234,685
Financing receivable, originated three years before latest fiscal year						1,116,969
Financing receivable, originated four years before latest fiscal year							333,397
Financing receivable, originated five or more years before latest fiscal year	312,356
Loans receivable	9,509,007
Risk Rating Three [Member] | U.S. Loans [Member]
Financing receivable, originated in current fiscal year	586,916
Financing receivable, originated in fiscal year before latest fiscal year				2,404,636
Financing receivable, originated two years before latest fiscal year					1,625,490
Financing receivable, originated three years before latest fiscal year						1,116,969
Financing receivable, originated four years before latest fiscal year							229,517
Financing receivable, originated five or more years before latest fiscal year	228,698
Loans receivable	6,192,226
Risk Rating Three [Member] | Non-U.S. Loans [Member]
Financing receivable, originated in current fiscal year	96,634
Financing receivable, originated in fiscal year before latest fiscal year				2,423,414
Financing receivable, originated two years before latest fiscal year					430,690
Financing receivable, originated four years before latest fiscal year							103,880
Loans receivable	3,054,618
Risk Rating Three [Member] | Unique Loans [Member]
Financing receivable, originated two years before latest fiscal year					178,505
Financing receivable, originated five or more years before latest fiscal year	83,658
Loans receivable	262,163
Risk Rating Four [Member]
Loans receivable	2,951,069		$ 169,336
Risk Rating Four [Member] | Loans Receivable [Member]
Financing receivable, originated in current fiscal year	65,860
Financing receivable, originated in fiscal year before latest fiscal year				692,197
Financing receivable, originated two years before latest fiscal year					2,019,642
Financing receivable, originated three years before latest fiscal year						63,212
Financing receivable, originated four years before latest fiscal year							110,158
Loans receivable	2,951,069
Risk Rating Four [Member] | U.S. Loans [Member]
Financing receivable, originated in current fiscal year	65,860
Financing receivable, originated in fiscal year before latest fiscal year				165,782
Financing receivable, originated two years before latest fiscal year					1,042,967
Financing receivable, originated three years before latest fiscal year						$ 63,212
Financing receivable, originated four years before latest fiscal year							$ 110,158
Loans receivable	1,447,979
Risk Rating Four [Member] | Non-U.S. Loans [Member]
Financing receivable, originated in fiscal year before latest fiscal year				231,923
Loans receivable	231,923
Risk Rating Four [Member] | Unique Loans [Member]
Financing receivable, originated in fiscal year before latest fiscal year				$ 294,492
Financing receivable, originated two years before latest fiscal year					976,675
Loans receivable	1,271,167
Risk Rating Five [Member] | Loans Receivable [Member]
Financing receivable, originated two years before latest fiscal year					279,874
Financing receivable, originated five or more years before latest fiscal year	52,787
Loans receivable	332,661
Risk Rating Five [Member] | Impaired Loans [Member]
Financing receivable, originated two years before latest fiscal year					$ 279,874
Financing receivable, originated five or more years before latest fiscal year	52,787
Loans receivable	$ 332,661