Our accounts and notes receivable are recorded at cost. The portion of our notes receivable due in one year or less are included in accounts and notes receivable and the long-term portion is included in other assets, net. Lease receivables, which are included in notes receivable, arise from sales-type leases of products. We typically sell, without recourse, the contractual right to the lease payment stream to third parties. For certain customers we retain the lease.

The contractual amounts due under our leases as of December 31, 2011 were as follows (table in thousands):

Year	Contractual amounts due under leases
2012	$	126,598
2013		108,242
2014		99,389
Thereafter		1,231
Total		335,460
Less amounts representing interest		(6,856)
Present value		328,604
Current portion (included in accounts and notes receivable)		123,896
Long-term portion (included in other assets, net)	$	204,708

Subsequent to December 31, 2011, we sold $92.3 million of these notes to third parties without recourse.

We maintain an allowance for credit losses on our accounts and notes receivable. The allowance is based on the credit worthiness of our customers, including an assessment of the customer's financial position, operating performance and their ability to meet their contractual obligation. We assess the credit scores for our customers each quarter. In addition, we consider our historical experience, the age of the receivable and current market and economic conditions. Uncollectible amounts are charged against the allowance account.

In the event we determine that a lease may not be paid, we include in our allowance an amount for the outstanding balance related to the lease receivable. As of December 31, 2011, amounts from lease receivables past due for more than 90 days were not significant.

The following table presents the activity of our allowance for credit losses related to lease receivables for the years ended December 31, 2011 and 2010 (table in thousands):

	December 31, 2011		December 31, 2010
Balance, beginning of the year	$	44,661	$	40,199
Recoveries		(31,531)		(25,171)
Provisions		11,117		29,633
Balance, end of the year	$	24,247	$	44,661

Gross lease receivables totaled $335.5 million and $278.4 million in 2011 and 2010, respectively, before the allowance. The components of these balances were individually evaluated for impairment by management.