Loans and Allowance for Losses and Concentrations of Credit Risk - Loan (Details) - USD ($)
$ in Thousands |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans held for investment, at amortized cost |
|
$ 3,258,413
|
$ 2,833,461
|
| Allowance for Loan and Lease Losses, Real Estate |
|
4,480
|
5,864
|
| Total loans, net of allowance |
|
3,962,044
|
3,520,075
|
| Unsecuritized [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
[1] |
3,257,990
|
2,837,080
|
| Unamortized premiums, discounts and other cost basis adjustments |
|
423
|
(3,619)
|
| Loans held for investment, at amortized cost |
|
3,258,413
|
2,833,461
|
| Allowance for Loan and Lease Losses, Real Estate |
|
3,736
|
5,324
|
| Total loans, net of allowance |
|
3,254,677
|
2,828,137
|
| Unsecuritized [Member] | Farm & Ranch [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
|
2,249,864
|
2,118,867
|
| Unsecuritized [Member] | Rural Utilities [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
|
1,008,126
|
718,213
|
| In Consolidated Trusts |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
[1] |
708,111
|
688,751
|
| Unamortized premiums, discounts and other cost basis adjustments |
|
0
|
3,727
|
| Loans held for investment, at amortized cost |
|
708,111
|
692,478
|
| Allowance for Loan and Lease Losses, Real Estate |
|
744
|
540
|
| Total loans, net of allowance |
|
707,367
|
691,938
|
| In Consolidated Trusts | Farm & Ranch [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
|
708,111
|
421,355
|
| In Consolidated Trusts | Rural Utilities [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
|
0
|
267,396
|
| Loans [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
[1] |
3,966,101
|
3,525,831
|
| Unamortized premiums, discounts and other cost basis adjustments |
|
423
|
108
|
| Loans held for investment, at amortized cost |
|
3,966,524
|
3,525,939
|
| Allowance for Loan and Lease Losses, Real Estate |
|
4,480
|
5,864
|
| Total loans, net of allowance |
|
3,962,044
|
3,520,075
|
| Loans [Member] | Farm & Ranch [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
|
2,957,975
|
2,540,222
|
| Loans [Member] | Rural Utilities [Member] |
|
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
|
| Loans and Lease Receivable Unpaid Principal Balance |
|
$ 1,008,126
|
$ 985,609
|
|
|