Derivative Financial Instruments Derivative Financial Instruments - Schedule of LIBOR interest rate caps (Details) - USD ($)	Jun. 30, 2019	May 15, 2019	Dec. 31, 2018	Dec. 11, 2018	Jul. 16, 2018	Mar. 07, 2018	Nov. 28, 2017	Sep. 18, 2017	Jun. 23, 2017
Derivative [Line Items]
Notional Amount	$ 647,326,000		$ 513,208,000
Interest Rate Caps | LIBOR
Derivative [Line Items]
Notional Amount	400,000,000	$ 100,000,000		$ 50,000,000	$ 50,000,000	$ 50,000,000	$ 50,000,000	$ 50,000,000	$ 50,000,000
Strike Rate		2.50%		2.75%	2.50%	2.25%	1.50%	1.50%	1.50%
Premium Paid	$ 1,839,000	$ 288,000		$ 210,000	$ 319,000	$ 310,000	$ 359,000	$ 199,000	$ 154,000