Securitizations and Term Debt Financings (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012		Dec. 31, 2011
Outstanding amounts of secured and unsecured term debt financings
Total secured debt financings	$ 1,924,435		$ 2,535,759
Total unsecured debt financings	1,250,700		450,757
Total secured and unsecured debt financings	3,175,135		2,986,516
Securitization No. 1 [Member]
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Effective interest rate	0.51%	[1]
Secured debt financings, Maturity date	Jun. 20, 2031	[2]
Total secured debt financings	361,278		387,124
Securitization No. 2 [Member]
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Effective interest rate	0.55%	[1]
Secured debt financings, Maturity date	Jun. 14, 2037	[2]
Total secured debt financings	850,532		891,452
Term Financing No. 1 [Member]
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Effective interest rate	0.00%	[1]
Total secured debt financings	0		595,076
ECA Term Financings [Member]
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Minimum effective interest rate	2.65%	[1]
Secured debt financings, Maximum effective interest rate	3.96%	[1]
Secured debt financings, Maturity date start	12/3/2021	[2]
Secured debt financings, Maturity date end	4/3/2024	[2]
Total secured debt financings	593,216		536,107
Bank financings
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Minimum effective interest rate	4.22%	[1]
Secured debt financings, Maximum effective interest rate	4.57%	[1]
Secured debt financings, Maturity date start	9/15/2015	[2]
Secured debt financings, Maturity date end	10/26/2017	[2]
Total secured debt financings	119,409		126,000
Senior Notes Due Two Thousand Seventeen [Member]
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Effective interest rate	6.75%	[1]
Secured debt financings, Maturity date	Apr. 15, 2017	[2]
Total unsecured debt financings	500,000		0
Senior Notes due 2018
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Effective interest rate	9.75%	[1]
Secured debt financings, Maturity date	Aug. 01, 2018	[2]
Total unsecured debt financings	450,700		450,757
Senior Notes Due Two Thousand Twenty [Member]
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Effective interest rate	7.625%	[1]
Secured debt financings, Maturity date	Apr. 15, 2020	[2]
Total unsecured debt financings	300,000		0
2010 Revolving Credit Facility [Member]
Outstanding amounts of secured and unsecured term debt financings
Secured debt financings, Maturity date	Sep. 28, 2013	[2]
Total unsecured debt financings	$ 0		$ 0

[1] Reflects floating rate in effect at the applicable reset date plus the margin except for the ECA Term Financings, Bank Financings and the Senior Notes due 2017, 2018 and 2020, which are fixed rate.

[2] For Securitization No. 1 and Securitization No. 2, all cash flows available after expenses and interest is applied to debt amortization.