The Company invests in agency securities, corporate securities, asset-backed securities, treasury securities and other securities. The following is a summary of amounts recorded on the Consolidated Balance Sheet for marketable securities (current and non-current).

		June 30,		December 31,
(Millions)		2013		2012

U.S. government agency securities		$	158	$	162
Foreign government agency securities			11		16
Corporate debt securities			283		471
Commercial paper			165		116
Certificates of deposit/time deposits			57		41
U.S. treasury securities			54		54
U.S. municipal securities			12		13
Asset-backed securities:
	Automobile loan related		479		567
	Credit card related		38		123
	Equipment lease related		42		54
	Other		11		31
Asset-backed securities total			570		775

Current marketable securities		$	1,310	$	1,648

U.S. government agency securities		$	207	$	125
Foreign government agency securities			62		51
Corporate debt securities			523		494
Certificates of deposit/time deposits			20		―
U.S. treasury securities			49		18
U.S. municipal securities			―		14
Auction rate securities			10		7
Asset-backed securities:
	Automobile loan related		417		375
	Credit card related		117		34
	Equipment lease related		81		36
	Other		56		8
Asset-backed securities total			671		453

Non-current marketable securities		$	1,542	$	1,162

Total marketable securities		$	2,852	$	2,810

Classification of marketable securities as current or non-current is dependent upon management's intended holding period, the security's maturity date and liquidity considerations based on market conditions. If management intends to hold the securities for longer than one year as of the balance sheet date, they are classified as non-current. At June 30, 2013, gross unrealized losses totaled approximately $10 million (pre-tax), while gross unrealized gains totaled approximately $1 million (pre-tax). At December 31, 2012, gross unrealized losses totaled approximately $6 million (pre-tax), while gross unrealized gains totaled approximately $3 million (pre-tax). Refer to Note 4 for a table that provides the net realized gains (losses) related to sales or impairments of debt and equity securities, which includes marketable securities. The gross amounts of the realized gains or losses were not material. Cost of securities sold use the first in, first out (FIFO) method. Since these marketable securities are classified as available-for-sale securities, changes in fair value will flow through other comprehensive income, with amounts reclassified out of other comprehensive income into earnings upon sale or “other-than-temporary” impairment.

3M reviews impairments associated with its marketable securities in accordance with the measurement guidance provided by ASC 320, Investments-Debt and Equity Securities, when determining the classification of the impairment as “temporary” or “other-than-temporary”. A temporary impairment charge results in an unrealized loss being recorded in the other comprehensive income component of shareholders' equity. Such an unrealized loss does not reduce net income attributable to 3M for the applicable accounting period because the loss is not viewed as other-than-temporary. The factors evaluated to differentiate between temporary and other-than-temporary include the projected future cash flows, credit ratings actions, and assessment of the credit quality of the underlying collateral, as well as other factors.

The balances at June 30, 2013 for marketable securities by contractual maturity are shown below. Actual maturities may differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties.

3M has a diversified marketable securities portfolio with a fair market value of $2.852 billion as of June 30, 2013. Within this portfolio, current and long-term asset-backed securities (estimated fair value of $1.241 billion) primarily include interests in automobile loans, credit cards and equipment leases. 3M's investment policy allows investments in asset-backed securities with minimum credit ratings of Aa2 by Moody's or AA by S&P or Fitch. At June 30, 2013, all asset-backed security investments were in compliance with this policy. Approximately 99 percent of all asset-backed security investments were rated AAA or A-1+ by Standard & Poor's and/or Aaa or P-1 by Moody's and/or AAA or F1+ by Fitch.

3M's marketable securities portfolio includes auction rate securities that represent interests in investment grade credit default swaps; however, currently these holdings comprise less than one percent of this portfolio. The estimated fair value of auction rate securities was $10 million at June 30, 2013 and $7 million at December 31, 2012. Gross unrealized losses within accumulated other comprehensive income related to auction rate securities totaled $3 million (pre-tax) at June 30, 2013 and $6 million (pre-tax) at December 31, 2012. As of June 30, 2013, auction rate securities associated with these balances have been in a loss position for more than 12 months. Since the second half of 2007, these auction rate securities failed to auction due to sell orders exceeding buy orders. Liquidity for these auction-rate securities is typically provided by an auction process that resets the applicable interest rate at pre-determined intervals, usually every 7, 28, 35, or 90 days. The funds associated with failed auctions will not be accessible until a successful auction occurs or a buyer is found outside of the auction process. Refer to Note 10 for a table that reconciles the beginning and ending balances of auction rate securities.