Derivative Financial Instruments and Hedging Activities - Narrative (Details)	12 Months Ended
Dec. 31, 2017 contract	Sep. 30, 2019 USD ($)
Derivative [Line Items]
Debt instrument, face amount		$ 270,000,000.0
Cash collateral held by counterparties subject to master netting agreements		$ 15,700,000
Interest Rate Swap
Derivative [Line Items]
Derivative, instruments terminated \| contract	2

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant