Financial Instruments Level within the Fair Value Hierarchy (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Assets:
Short-term investments	$ 434,175
Fixed maturities - available for sale	1,032,215
Preferred stock	24,212
Common stock	38,911
Derivatives	1,165
Total	1,530,678
Liabilities:
Guaranteed residual values of TRAC leases	0
Derivatives	51,550	59,313
Other obligations	0
Total	51,550
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Short-term investments	434,175
Fixed maturities - available for sale	951,598
Preferred stock	24,212
Common stock	38,911
Derivatives	0
Total	1,448,896
Liabilities:
Guaranteed residual values of TRAC leases	0
Derivatives	0
Other obligations	0
Total	0
Significant Other Observable Inputs (Level 2)
Assets:
Short-term investments	0
Fixed maturities - available for sale	79,437
Preferred stock	0
Common stock	0
Derivatives	1,165
Total	80,602
Liabilities:
Guaranteed residual values of TRAC leases	0
Derivatives	51,550
Other obligations	0
Total	51,550
Significant Unobservable Inputs (Level 3)
Assets:
Short-term investments	0
Fixed maturities - available for sale	1,180
Preferred stock	0
Common stock	0
Derivatives	0
Total	1,180
Liabilities:
Guaranteed residual values of TRAC leases	0
Derivatives	0
Other obligations	0
Total	$ 0