Fair Value of Assets and Liabilities (Summary of Changes in Level Three Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Loans Held For Investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 33,717	$ 22,137
Total net gains (losses) included in Net income	(1,077)	1,025
Total net gains (losses) included in Other comprehensive income	0	0
Issuances	0
Sales	0
Settlements	(28,367)	(13,219)
Net transfers into/(out of) Level 3	7,074	23,774
Ending Balance	11,347	33,717
Mortgage Servicing Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	33,676	19,103
Total net gains (losses) included in Net income	27,701	14,573
Purchases	13,806
Issuances	0
Sales	0
Ending Balance	75,183	33,676
Derivative Financial Instruments, Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	2,157	2,291
Total net gains (losses) included in Net income	300	(134)
Total net gains (losses) included in Other comprehensive income	0
Issuances	0
Sales	0
Ending Balance	2,457	2,157
Municipal
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	77,181	79,626
Total net gains (losses) included in Other comprehensive income	(8,541)	(501)
Purchases	63,644	33,593
Issuances	0
Sales	0
Settlements	(23,358)	(35,537)
Ending Balance	108,926	77,181
U.S. Government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,779	0
Total net gains (losses) included in Other comprehensive income	(314)	(504)
Issuances	0
Sales	0
Settlements	(315)
Net transfers into/(out of) Level 3		4,283
Ending Balance	$ 3,150	$ 3,779