Mortgage Banking Operations - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Servicing Advances	$ 4.9	$ 5.3
Multifamily DUS [Member]
Financing Receivable, Impaired [Line Items]
Weighted average life of company's multifamily MSRs	10 years 3 months 25 days
Early buyout loans [Member]
Financing Receivable, Impaired [Line Items]
Loans Receivable, in Ginnie Mae pool	$ 47.9	$ 39.3

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans held for sale. Excludes loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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