4. Investment Securities

Investment securities at December 31, 2014 and 2013 are as follows:

2014	Amortized cost		Unrealized gains		Unrealized losses		Fair value
	(in thousands)
Available for sale securities:
Affiliated funds	$	162,425		4,237		(5,392)		161,270

	$	162,425		4,237		(5,392)		161,270


Trading securities:
Mortgage-backed securities								28
Common stock								72
Affiliated funds								81,913

								82,013


Total investment securities								243,283

2013	Amortized cost		Unrealized gains		Unrealized losses		Fair value
	(in thousands)
Available for sale securities:
Mortgage-backed securities	$	8		1		—		9
Corporate bonds		14,568		61		—		14,629
Affiliated funds		87,710		5,899		(957)		92,652

	$	102,286		5,961		(957)		107,290


Trading securities:
Mortgage-backed securities								37
Municipal bonds								501
Corporate bonds								9,412
Common stock								60
Affiliated funds								84,048

								94,058


Total investment securities								201,348

A summary of available for sale affiliated funds with fair values below carrying values at December 31, 2014 is as follows:

	Less than 12 months				12 months or longer				Total
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
	(in thousands)
Affiliated funds	$	66,858		(5,362)		1,187		(30)		68,045		(5,392)

Total temporarily impaired securities	$	66,858		(5,362)		1,187		(30)		68,045		(5,392)

Based upon our assessment of these affiliated funds, the time frame investments have been in a loss position and our intent to hold the affiliated funds until they have recovered, we determined that a write-down was not necessary at December 31, 2014.

Corporate bonds accounted for as available for sale and trading matured in 2014. Mortgage-backed securities accounted for as available for sale were called in 2014. Mortgage-backed securities accounted for as trading and held as of December 31, 2014 mature in 2022.

Investment securities with fair values of $301.0 million, $442.0 million and $79.9 million were sold during 2014, 2013 and 2012, respectively. During 2014, net realized gains of $5.1 million and $4.1 million were recognized from the sale of $149.8 million in available for sale securities and the sale of $151.2 million in trading securities, respectively. During 2013, net realized gains of $14.4 million and $7.7 million were recognized from the sale of $247.0 million in available for sale securities and the sale of $195.0 million in trading securities, respectively. During 2012, net realized gains of $3.2 million and $5.3 million were recognized from the sale of $32.9 million in available for sale securities and the sale of $47.0 million in trading securities, respectively.

Accounting standards establish a framework for measuring fair value and a three-level hierarchy for fair value measurements based upon the transparency of inputs to the valuation of the asset. Inputs may be observable or unobservable and refer broadly to the assumptions that market participants would use in pricing the asset. An individual investment's fair value measurement is assigned a level based upon the observability of the inputs that are significant to the overall valuation. The three-level hierarchy of inputs is summarized as follows:

•	Level 1—Investments are valued using quoted prices in active markets for identical securities.
•	Level 2—Investments are valued using other significant observable inputs, including quoted prices in active markets for similar securities.
•	Level 3—Investments are valued using significant unobservable inputs, including the Company's own assumptions in determining the fair value of investments.

Assets classified as Level 2 can have a variety of observable inputs. These observable inputs are collected and utilized, primarily by an independent pricing service, in different evaluated pricing approaches depending upon the specific asset to determine a value. The fair value of municipal bonds is measured based on pricing models that take into account, among other factors, information received from market makers and broker/dealers, current trades, bid-wants lists, offerings, market movements, the callability of the bond, state of issuance and benchmark yield curves. The fair value of corporate bonds is measured using various techniques, which consider recently executed transactions in securities of the issuer or comparable issuers, market price quotations (where observable), bond spreads and fundamental data relating to the issuer. The fair value of equity derivatives is measured based on active market broker quotes, evaluated broker quotes and evaluated prices from vendors.

Securities' values classified as Level 3 are primarily determined through the use of a single quote (or multiple quotes) from dealers in the securities using proprietary valuation models. These quotes involve significant unobservable inputs, and thus, the related securities are classified as Level 3 securities.

The following tables summarize our investment securities as of December 31, 2014 and 2013 that are recognized in our consolidated balance sheets using fair value measurements based on the differing levels of inputs. There were no transfers between levels for the years ended December 31, 2014 or 2013.

2014	Level 1		Level 2		Level 3		Total

	(in thousands)
Mortgage-backed securities	$	—		28		—		28
Common stock		72		—		—		72
Affiliated funds		243,183		—		—		243,183

Total	$	243,255	$	28	$	—	$	243,283

2013	Level 1		Level 2		Level 3		Total

	(in thousands)
Mortgage-backed securities		—		46		—		46
Municipal bonds		—		501		—		501
Corporate bonds		—		24,041		—		24,041
Common stock		60		—		—		60
Affiliated funds		176,700		—		—		176,700

Total	$	176,760	$	24,588	$	—	$	201,348