Available-for-sale investments (Tables)

12 Months Ended

Dec. 31, 2011

Available-for-sale investments [Abstract]

Amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of available-for-sale investments by type of security

Type of security as of December 31, 2011	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
U.S. Treasury securities	$	3,878	$	68	$	—		$	3,946
Other government-related debt securities:
Obligations of U.S. government agencies and FDIC-guaranteed bank debt		1,548		23		—			1,571
Foreign and other		441		9		—			450
Corporate debt securities:
Financial		2,493		30		(15	)		2,508
Industrial		3,077		79		(10	)		3,146
Other		280		9		-			289
Mortgage- and asset-backed securities		1,789		6		(10	)		1,785
Money market mutual funds		6,266		—		—			6,266
Total debt security investments		19,772		224		(35	)		19,961
Equity securities		42		—		—			42
Total available-for-sale investments	$	19,814	$	224	$	(35	)	$	20,003

Type of security as of December 31, 2010	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
U.S. Treasury securities	$	5,044	$	50	$	(14	)	$	5,080
Other government-related debt securities:
Obligations of U.S. government agencies and FDIC-guaranteed bank debt		2,158		51		(1	)		2,208
Foreign and other		837		16		(1	)		852
Corporate debt securities:
Financial		2,252		53		(9	)		2,296
Industrial		2,441		71		(5	)		2,507
Other		307		10		(1	)		316
Mortgage- and asset-backed securities		841		5		(5	)		841
Money market mutual funds		3,030		—		—			3,030
Other short-term interest-bearing securities		147		—		—			147
Total debt security investments		17,057		256		(36	)		17,277
Equity securities		50		—		(2	)		48
Total available-for-sale investments	$	17,107	$	256	$	(38	)	$	17,325

Fair values of available-for-sale investments by classification in the consolidated balance sheets

Classification in the Consolidated Balance Sheets	2011		2010
Cash and cash equivalents	$	6,266	$	3,142
Marketable securities		13,695		14,135
Other assets — noncurrent		42		48
Total available-for-sale investments	$	20,003	$	17,325

Fair values of available-for-sale debt security investments by contractual maturity

Contractual maturity	2011		2010
Maturing in one year or less	$	6,811	$	4,118
Maturing after one year through three years		6,346		6,736
Maturing after three years through five years		5,710		5,812
Maturing after five years		1,094		611
Total debt securities	$	19,961	$	17,277