Consolidated Statements of Cash Flows (Parenthetical) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Statement Of Cash Flows [Abstract]
Underwriting discounts, commissions and costs	$ 2.6

Expense related to distribution, servicing and underwriting fees.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14)
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Name:	us-gaap_ExpenseRelatedToDistributionOrServicingAndUnderwritingFees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration