Summary of Significant Accounting Policies (Supplemental Consolidated Statements of Cash Flows Information) (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Supplemental disclosure of cash activities:
Cash paid for interest	$ 5,745,000	$ 5,303,000
Supplemental disclosure of non-cash activities:
Capitalization of interest and financing costs	$ 258,000	$ 358,000

Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4297-108586

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration