Mortgage Loan Losses Allowance - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Mortgage Loan Loss Allowance [Abstract]
Pre-tax charges for loan losses related to mortgage loans sold	$ 2,400us-gaap_ProvisionForLoanLossesExpensed	$ 2,300us-gaap_ProvisionForLoanLossesExpensed	$ 1,300us-gaap_ProvisionForLoanLossesExpensed
Mortgage loan loss allowance	$ 10,000	$ 8,200

Amount of expense related to loss from loan transactions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 9

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.11)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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