Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Name:	us-gaap_RestrictedCashAndCashEquivalentsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Cash, Cash Equivalents, and Restricted Cash (Schedule of Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash And Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 108,309	$ 143,444	$ 68,783
Restricted cash - current asset	30,243	32,464
Total cash, cash equivalents, and restricted cash	141,120	178,300	104,295	$ 185,970
Securitization Escrow Accounts [Member] \| Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - current asset	30,046	32,261	32,699
Payment and Performance Bonds [Member] \| Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - current asset	197	203	225
Surety Bonds and Workers Compensation [Member] \| Other Assets - Noncurrent [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - noncurrent asset	$ 2,568	$ 2,392	$ 2,588