Fair Values of Assets and Liabilities (Summary of Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Loans held-for- investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 11,249	$ 26,620	$ 11,347	$ 33,717
Net Income	118	(260)	285	(1,388)
Other comprehensive loss	0	0	0	0
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	(886)	(16,402)	(1,351)	(22,657)
Net transfers into/(out of) Level 3	0	3,806	200	4,092
Ending Balance	10,481	13,764	10,481	13,764
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	71,022	54,572	75,183	33,676
Net Income	1,421	8,622	(2,740)	15,712
Other comprehensive loss		0
Purchases	407	0	407	13,806
Issuances	0	0	0	0
Settlements		0
Net transfers into/(out of) Level 3	0	0	0	0
Ending Balance	72,850	63,194	72,850	63,194
Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,089	4,605	2,457	2,157
Net Income	507	(786)	1,139	1,662
Other comprehensive loss	0	0	0	0
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Net transfers into/(out of) Level 3	0	0	0	0
Ending Balance	3,596	3,819	3,596	3,819
Municipal Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	103,834	84,592	108,926	77,181
Net Income		0
Other comprehensive loss	6,519	(895)	8,056	(3,085)
Purchases	555	14,746	1,524	27,016
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	(612)	(1,877)	(8,210)	(4,546)
Net transfers into/(out of) Level 3		0
Ending Balance	110,296	96,566	110,296	96,566
U.S. Government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	2,993	3,616	3,150	3,779
Net Income	0	0	0	0
Other comprehensive loss	142	(134)	143	(297)
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	(158)	0	(316)	0
Net transfers into/(out of) Level 3	0	0	0	0
Ending Balance	$ 2,977	$ 3,482	$ 2,977	$ 3,482

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-SubTopic 10
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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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