Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Measurements [Abstract]

Assets and Liabilities Measured at Fair Value on Recurring Basis

	As of December 31, 2017									As of December 31, 2016
	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)		$	192,868	$	—	$	—	$	192,868	$	146,103	$	—	$	—	$	146,103
Restricted cash(a)			4,780		—		—		4,780		50,504		—		—		50,504
Investments in lieu of retainage(b)			69,891		2,405		—		72,296		46,855		4,411		—		51,266
Total		$	267,539	$	2,405	$	—	$	269,944	$	243,462	$	4,411	$	—	$	247,873

(a)Includes money market funds with original maturity dates of three months or less.

(b)Investments in lieu of retainage are included in accounts receivable and are comprised of money market funds and municipal bonds, the majority of which are rated A3 or better. 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. All of the above investments are available-for-sale securities.