The Company invests in certain limited partnerships that are formed to develop and operate apartment complexes designed as high-quality affordable housing for lower income tenants throughout the United States. The Company's ownership amount in each limited partnership varies. Each of the partnerships must meet the regulatory requirements for affordable housing for a minimum 15-year compliance period to fully utilize the tax credits. Depending on the ownership percentage and the influence the Company has on the limited partnership, the company uses either the equity method or cost method of accounting. The limited partnerships are being amortized over the lives of the related tax credit. If the partnerships cease to qualify during the compliance period, the credits may be denied for any period in which the projects are not in compliance and a portion of the credits previously taken may be subject to recapture with interest.

The Company finances the purchase of certain real estate tax credits generated by partnerships which own multiple properties currently under construction. These transactions were financed with non-recourse notes which are collateralized by the Company's partnership interests in the real estate investment tax credits. The notes are payable upon demand and, if defaulted, interest will be imposed at the annual respective rate or the maximum rate permitted by applicable law. No interest is due if the notes are paid on demand. The Company has no liabilities in addition to these notes payable or any contingent liabilities to the partnerships.

	December 31,

	2011				2010
	Amount		Count		Amount		Count
	(Dollars in thousands)
Tax credit partnerships:
Equity method	$	94,874		26	$	111,593		29
Cost method		48,587		17		43,481		17

Total tax credit partnerships		143,461		43		155,074		46
Tax exempt bonds		984				—

Grand total	$	144,445			$	155,074

Notes payable	$	52,434			$	49,690
Remaining tax credits	$	183,186			$	168,521

The Company's usage of federal tax credits approximated $11.1 million, $12.4 million and $7.1 million during 2011, 2010 and 2009, respectively. Investment amortization amounted to $14.6 million, $9.4 million and $7.0 million for the years ended December 31, 2011, 2010 and 2009, respectively. During 2011 the Company recorded $1.3 million of impairment on certain investments. Also during 2011 the Company sold three investments totaling $25.7 million with a loss of $3.7 million, compared to, one investment sold in 2010 totaling $3.2 million with a loss of $1.2 million. The Company recorded a purchase accounting adjustment in 2010 which reduced the affordable housing investments acquired through the UCB acquisition by $3.0 million.