Derivatives - Interest Rate Cap (Details) - Interest rate cap $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Derivatives
Number of financial institutions entered into derivative contracts \| item	2
Derivatives not designated as hedging instruments
Derivatives
Collateral balances held \| $	$ 0.2	$ 0.3

The carrying amount (fair value) as of the balance sheet date of securities held that had been pledged by counterparties under financing and lending arrangements, pursuant to which the entity has the right by agreement or custom to sell or re-pledge such securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5086-111524

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