Valuation and qualifying accounts (Tables)

12 Months Ended

Dec. 31, 2012

Valuation and qualifying accounts

Schedule of valuation and qualifying accounts

	Balance at beginning of year		Additions charged to earnings		Changes to reserve, net(1)			Balance at end of year
Year ended December 31, 2012
Allowance for doubtful accounts	$	1,247	$	259	$	(906	)	$	600
Reserves for inventory		1,288		715		(804	)		1,199
Valuation of deferred tax assets		830		—		544			1,374
Year ended December 31, 2011
Allowance for doubtful accounts	$	1,200	$	1,106	$	(1,059	)	$	1,247
Reserves for inventory		1,404		1,080		(1,196	)		1,288
Valuation of deferred tax assets		877		—		(47	)		830
Year ended December 31, 2010
Allowance for doubtful accounts	$	755	$	966	$	(521	)	$	1,200
Reserves for inventory		1,931		930		(1,457	)		1,404
Valuation of deferred tax assets		566		343		(32	)		877

(1)

Deductions from the allowance for doubtful accounts equal accounts receivable written off, less recoveries, against the allowance. Deductions from the reserves for inventory excess and obsolete items equal inventory written off against the reserve as items were disposed of. Deductions to the valuation of deferred tax assets relate to the reversals due to changes in management's judgments regarding the future realization of the underlying deferred tax assets.