Cash, Cash Equivalents, and Restricted Cash (Schedule of Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Restricted Cash And Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 271,874	$ 108,309
Restricted cash - current asset	61,572	30,243
Total cash, cash equivalents, and restricted cash	335,973	141,120	$ 158,680	$ 178,300
Securitization Escrow Accounts [Member] | Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - current asset	61,417	30,046
Payment and Performance Bonds [Member] | Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - current asset	155	197
Surety Bonds and Workers Compensation [Member] | Other Assets - Noncurrent [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - noncurrent asset	$ 2,527	$ 2,568