Cash, Cash Equivalents, and Restricted Cash (Narrative) (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Restricted Cash And Cash Equivalents Items [Line Items]
Surety, payment and performance bonds	$ 42,000,000.0	$ 41,800,000
Collateral payment for performance bonds	0	0
Workers Compensation Policy [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Collateral	$ 2,300,000	$ 2,300,000

The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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