Cash, Cash Equivalents, Short-Term Investments, Restricted Cash Equivalents and Investments

Cash and cash equivalents, short-term investments, and restricted cash equivalents and investments as of September 30, 2013, consisted of the following (in thousands):



	Amortized Cost		Estimated Fair Value
Cash and cash equivalents:
Cash	$	39,348	$	39,348
Money market mutual funds	23,038		23,038
Corporate notes and bonds	72,494		72,493
Total cash and cash equivalents	134,880		134,879
Short-term investments:
Corporate notes and bonds	60,005		60,041
U.S. government agency securities	23,478		23,486
Total short-term investments	83,483		83,527
Total cash, cash equivalents and short-term investments	$	218,363	$	218,406
Restricted cash equivalents and investments	$	5,000	$	5,000

Cash and cash equivalents, short-term investments, and restricted cash equivalents and investments as of December 31, 2012 consisted of the following (in thousands):



	Amortized Cost		Estimated Fair Value
Cash and cash equivalents:
Cash	$	71,283	$	71,283
Money market mutual funds	10,680		10,680
Corporate notes and bonds	81,237		81,235
Total cash and cash equivalents	163,200		163,198



Short-term investments:
Corporate notes and bonds	65,426		65,502
U.S. Government agency securities	42,693		42,714
Total short-term investments	108,119		108,216
Total cash, cash equivalents, and short-term investments	$	271,319	$	271,414
Restricted cash equivalents and investments	$	10,000	$	10,000

Restricted cash equivalents and investments amounts as of September 30, 2013, and December 31, 2012 relate to cash and investments pledged as collateral against letters of credit in connection with lease agreements.

Realized gains or losses on sales of short-term investment securities for the quarters and nine months ended September 30, 2013 and 2012 were not significant. Gross unrealized gains and gross unrealized losses on short-term investment securities as of September 30, 2013 and December 31, 2012 were not significant.

Investments with remaining contractual maturities of five years or less are classified as short-term because the investments are marketable and highly liquid and we have the ability to utilize them for current operations. Contractual maturities of short-term investments as of September 30, 2013 (in thousands):



	Estimated Fair Value
Within one year	$	57,321
Between one year and five years	26,206
Total short-term investments	$	83,527