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 March 31, 2013, consisted of the following (in thousands):



	Amortized Cost		Estimated Fair Value
Cash and cash equivalents:
Cash	$	50,214	$	50,214
Money market mutual funds	6,979		6,978
Corporate notes and bonds	79,505		79,502
Total cash and cash equivalents	136,698		136,694
Short-term investments:
Corporate notes and bonds	88,693		88,766
U.S. government agency securities	35,111		35,128
Total short-term investments	123,804		123,894
Total cash, cash equivalents and short-term investments	$	260,502	$	260,588
Restricted cash equivalents and investments	$	10,000	$	10,000

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

Substantially all of the restricted cash equivalents and investments amounts as of March 31, 2013, and December 31, 2012 relate to cash and investments pledged as collateral against a letter of credit in connection with lease agreements.

Realized gains or losses on sales of short-term investment securities for the quarters ended March 31, 2013 and 2012 were not significant. Gross unrealized gains and gross unrealized losses on short-term investment securities as of March 31, 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 March 31, 2013 (in thousands):



	Estimated Fair Value
Within one year	$	99,791
Between one year and five years	24,103
Total short-term investments	$	123,894