Financial Instruments Level within the Fair Value Hierarchy (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Assets:
Short-term investments	$ 457,723	$ 434,175
Fixed maturities - available for sale	1,099,467	1,032,215
Preferred stock	17,533	24,212
Common stock	21,275	38,911
Derivatives	3,868	1,165
Total	1,599,866	1,530,678
Liabilities:
Guaranteed residual values of TRAC leases	0	0
Derivatives	32,716	51,550
Total	32,716	51,550
Level 1 [Member]
Assets:
Short-term investments	457,723	434,175
Fixed maturities - available for sale	898,209	951,598
Preferred stock	17,533	24,212
Common stock	21,275	38,911
Derivatives	3,868	0
Total	1,398,608	1,448,896
Liabilities:
Guaranteed residual values of TRAC leases	0	0
Derivatives	0	0
Total	0	0
Level 2 [Member]
Assets:
Short-term investments	0	0
Fixed maturities - available for sale	200,154	79,437
Preferred stock	0	0
Common stock	0	0
Derivatives	0	1,165
Total	200,154	80,602
Liabilities:
Guaranteed residual values of TRAC leases	0	0
Derivatives	32,716	51,550
Total	32,716	51,550
Level 3 [Member]
Assets:
Short-term investments	0	0
Fixed maturities - available for sale	1,104	1,180
Preferred stock	0	0
Common stock	0	0
Derivatives	0	0
Total	1,104	1,180
Liabilities:
Guaranteed residual values of TRAC leases	0	0
Derivatives	0	0
Total	$ 0	$ 0