Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Measurements [Abstract]

Assets and Liabilities Measured at Fair Value on Recurring Basis

	As of December 31, 2019									As of December 31, 2018
	Fair Value Hierarchy									Fair Value Hierarchy
(in thousands)		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Cash and cash equivalents(a)		$	193,685	$	—	$	—	$	193,685	$	116,075	$	—	$	—	$	116,075
Restricted cash(a)			8,416		—		—		8,416		3,788		—		—		3,788
Restricted investments(b)			—		70,974		—		70,974		—		58,142		—		58,142
Investments in lieu of retainage(c)			89,572		1,219		—		90,791		62,858		1,190		—		64,048
Total		$	291,673	$	72,193	$	—	$	363,866	$	182,721	$	59,332	$	—	$	242,053

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(a)Includes money market funds and short-term investments with maturity dates of three months or less when acquired.

(b)Restricted investments, as of December 31, 2019, consist of investments in corporate debt securities of $35.8 million, U.S. government agency securities of $33.8 million and corporate certificates of deposits of $1.4 million with maturities of up to five years, and are valued based on pricing models, which are determined from a compilation of primarily observable market information, broker quotes in non-active markets or similar assets and are therefore classified as Level 2 assets. As of December 31, 2018, restricted investments consisted of investments in corporate debt securities of $30.4 million and U.S. government agency securities of $27.7 million with maturities of up to five years. The amortized cost of these available-for-sale securities at December 31, 2019 and 2018 was not materially different from the fair value.

(c)Investments in lieu of retainage are included in retainage receivable and as of December 31, 2019 are comprised of money market funds of $89.6 million and municipal bonds of $1.2 million. The fair values of the money market funds are measured using quoted market prices; therefore, they are classified as Level 1 assets. The fair values of municipal bonds are measured using readily available pricing sources for comparable instruments; therefore, they are classified as Level 2 assets. As of December 31, 2018, investments in lieu of retainage consisted of money market funds of $62.9 million and municipal bonds of $1.2 million. The amortized cost of these available-for-sale securities at December 31, 2019 and 2018 was not materially different from the fair value.