Fair Value Measurements (Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Assets:
Cash and cash equivalents maturity period (maximum)	3 months
Fair Value, Measurements, Recurring
Assets:
Cash and cash equivalents	$ 380,564	$ 259,351
Restricted cash	14,116	14,480
Restricted investments	130,287	91,556
Investments in lieu of retainage	106,949	88,328
Total	631,916	453,715
Fair Value, Measurements, Recurring | Level 1
Assets:
Cash and cash equivalents	380,564	259,351
Restricted cash	14,116	14,480
Restricted investments	0	0
Investments in lieu of retainage	19,988	20,100
Total	414,668	293,931
Fair Value, Measurements, Recurring | Level 2
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Restricted investments	130,287	91,556
Investments in lieu of retainage	86,961	68,228
Total	217,248	159,784
Fair Value, Measurements, Recurring | Level 3
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Restricted investments	0	0
Investments in lieu of retainage	0	0
Total	0	0
Money Market Funds | Fair Value, Measurements, Recurring | Level 1
Assets:
Investments in lieu of retainage	20,000	20,100
Debt Securities | Fair Value, Measurements, Recurring | Level 2
Assets:
Investments in lieu of retainage	$ 87,000	$ 68,200