Allowance for Probable Loan Losses (By Loan Class) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Allowance for probable loan losses
Balance at the beginning of the period	$ 67,030	$ 61,384	$ 67,154	$ 61,384	$ 67,687
Losses charged to allowance	(12,044)		(2,458)	(14,879)	(5,335)
Recoveries credited to allowance	552		887	1,613	1,569
Net losses (recoveries) charged to allowance	(11,492)		(1,571)	(13,266)	(3,766)
Provision charged to operations	2,665		(2,730)	10,085	(1,068)
Balance at the end of the period	58,203	67,030	62,853	58,203	62,853
Watch - List Impaired
Allowance for probable loan losses
Losses charged to allowance	9,500	9,500
Commercial
Allowance for probable loan losses
Balance at the beginning of the period	11,412	12,596	20,691	12,596	27,905
Losses charged to allowance	(5,016)		(2,284)	(7,780)	(4,999)
Recoveries credited to allowance	408		447	1,046	1,030
Net losses (recoveries) charged to allowance	(4,608)		(1,837)	(6,734)	(3,969)
Provision charged to operations	4,976		(2,258)	5,918	(7,340)
Balance at the end of the period	11,780	11,412	16,596	11,780	16,596
Commercial Real Estate:Other Construction and Land Development
Allowance for probable loan losses
Balance at the beginning of the period	14,789	15,123	11,798	15,123	11,675
Losses charged to allowance					(1)
Recoveries credited to allowance	56		2	76	4
Net losses (recoveries) charged to allowance	56		2	76	3
Provision charged to operations	428		2,903	74	3,025
Balance at the end of the period	15,273	14,789	14,703	15,273	14,703
Commercial Real Estate: Farmland and Commercial
Allowance for probable loan losses
Balance at the beginning of the period	25,880	19,353	24,803	19,353	16,663
Losses charged to allowance	(6,878)		(70)	(6,879)	(70)
Recoveries credited to allowance	15		192	298	210
Net losses (recoveries) charged to allowance	(6,863)		122	(6,581)	140
Provision charged to operations	(1,988)		(6,629)	4,257	1,493
Balance at the end of the period	17,029	25,880	18,296	17,029	18,296
Commercial Real Estate: Multifamily
Allowance for probable loan losses
Balance at the beginning of the period	2,345	1,808	947	1,808	1,109
Provision charged to operations	(496)		627	41	465
Balance at the end of the period	1,849	2,345	1,574	1,849	1,574
Residential First Lien
Allowance for probable loan losses
Balance at the beginning of the period	3,546	3,467	3,006	3,467	2,950
Losses charged to allowance	(1)		(30)	(2)	(44)
Recoveries credited to allowance	10		1	11	2
Net losses (recoveries) charged to allowance	9		(29)	9	(42)
Provision charged to operations	72		614	151	683
Balance at the end of the period	3,627	3,546	3,591	3,627	3,591
Residential Junior Lien
Allowance for probable loan losses
Balance at the beginning of the period	7,745	7,719	4,689	7,719	6,103
Losses charged to allowance	(94)		(9)	(100)	(39)
Recoveries credited to allowance	55		229	157	295
Net losses (recoveries) charged to allowance	(39)		220	57	256
Provision charged to operations	(394)		1,884	(464)	434
Balance at the end of the period	7,312	7,745	6,793	7,312	6,793
Consumer
Allowance for probable loan losses
Balance at the beginning of the period	462	447	437	447	440
Losses charged to allowance	(55)		(65)	(118)	(182)
Recoveries credited to allowance	8		15	25	27
Net losses (recoveries) charged to allowance	(47)		(50)	(93)	(155)
Provision charged to operations	73		63	134	165
Balance at the end of the period	488	462	450	488	450
Foreign
Allowance for probable loan losses
Balance at the beginning of the period	851	871	783	871	842
Recoveries credited to allowance			1		1
Net losses (recoveries) charged to allowance			1		1
Provision charged to operations	(6)		66	(26)	7
Balance at the end of the period	$ 845	$ 851	$ 850	$ 845	$ 850

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount, after recoveries, of loans and leases that have been written-off.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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