Derivative Instruments and Hedging Activities - Additional Information (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2014 USD ($) instrument
Derivatives, Fair Value [Line Items]
Basis spread on variable rate	1.375%
Excess line of credit facility subject to interest rate risk	$ 50,000,000
Long-term debt, percentage bearing fixed interest, amount	200,000,000
Long-term debt, percentage bearing variable interest, amount	$ 92,000,000
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative, number of instruments held | instrument		2
Derivative, notional amount		$ 50,000,000
Derivative, amount of hedged item		50,000,000
Interest Rate Swap No. 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount		$ 25,000,000
Derivative, fixed interest rate		1.73%
Derivative, maturity date		Aug. 29, 2019
Interest Rate Swap No. 1 [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount		$ 25,000,000
Derivative, fixed interest rate		2.50%
Derivative, maturity date		Aug. 29, 2024
Maximum [Member]
Derivatives, Fair Value [Line Items]
Basis spread on variable rate	2.00%