Assets and liabilities subject to fair value measurements are as follows (in millions):


	As of March 31, 2019
	Level 1		Level 2		Level 3		Balance
Assets
Money market funds(1)	$	437.6	$	—	$	—	$	437.6
Time deposits(2)		—		38.4		—		38.4
U.S. government and agency securities(3)		—		1,111.1		—		1,111.1
Corporate debt securities(3)		—		111.7		—		111.7
Equity securities(4)		6.5		—		—		6.5
Total assets	$	444.1	$	1,261.2	$	—	$	1,705.3
Liabilities
Contingent consideration(5)		—		—		13.4		13.4
Total liabilities	$	—	$	—	$	13.4	$	13.4


	As of December 31, 2018
	Level 1		Level 2		Level 3		Balance
Assets
Money market funds(1)	$	247.6	$	—	$	—	$	247.6
Time deposits(2)		—		35.9		—		35.9
U.S. government and agency securities(3)		—		1,074.2		—		1,074.2
Corporate debt securities(3)		—		75.7		—		75.7
Equity securities(4)		3.5		—		—		3.5
Total assets	$	251.1	$	1,185.8	$	—	$	1,436.9
Liabilities
Contingent consideration(5)		—		—		13.4		13.4
Total liabilities	$	—	$	—	$	13.4	$	13.4

(1)

Included in cash and cash equivalents on the accompanying consolidated balance sheets.

(2)

Included in cash equivalents and current and non-current marketable investments on the accompanying consolidated balance sheets. The fair value of these securities is principally measured or corroborated by trade data for identical securities in which related trading activity is not sufficiently frequent to be considered a Level 1 input or comparable securities that are more actively traded.

(3)

Included in cash equivalents and current and non-current marketable investments on the accompanying consolidated balance sheets. Refer to Note 3—Investments—Available-for-Sale Investments for further information. The fair value of these securities is principally measured or corroborated by trade data for identical securities for which related trading activity is not sufficiently frequent to be considered a Level 1 input or comparable securities that are more actively traded.

(4)

Included in current marketable investments on the accompanying consolidated balance sheets. The fair value of these securities is based on quoted market prices for identical instruments in active markets.

(5)

Included in non-current liabilities on the accompanying consolidated balance sheets. The fair value of contingent consideration has been estimated using probability-weighted discounted cash flow models (DCFs). The DCFs incorporate Level 3 inputs including estimated discount rates that we believe market participants would consider relevant in pricing and the projected timing and amount of cash flows, which are estimated and developed, in part, based on the requirements specific to each acquisition agreement. The change in the fair value of contingent consideration for the three months ended March 31, 2019 was not material.