Available-for-Sale-Securities

The following table is a summary of available-for-sale securities recorded in cash and cash equivalents or marketable securities in our Consolidated Balance Sheets (in thousands):



	March 31, 2017								December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Money market funds	$	1,430.4	$	—	$	—	$	1,430.4	$	4,426.8	$	—	$	—	$	4,426.8
Municipal debt securities	—		—		—		—		—		—		—		—
Total	$	1,430.4	$	—	$	—	$	1,430.4	$	4,426.8	$	—	$	—	$	4,426.8

Estimated fair values of available-for-sale securities are generally based on prices obtained from commercial pricing services. The following table summarizes the classification of the available-for-sale debt securities on our Consolidated Balance Sheets (in thousands):



	March 31, 2017		December 31, 2016
Cash and cash equivalents	$	1,430.4	$	4,426.8
Total	$	1,430.4	$	4,426.8

The following table summarizes our portfolio of available-for-sale debt securities by contractual maturity (in thousands):



	March 31, 2017
	Amortized Cost		Estimated Fair Value
Less than one year	$	1,430.4	$	1,430.4
Greater than one year	—		—
Total	$	1,430.4	$	1,430.4