|
Trust Preferred Securities and Subordinated Debentures (Narrative) (Details) (USD $)
|
12 Months Ended |
|
|
Dec. 31, 2014
|
Dec. 31, 2013
|
| Subordinated Borrowing [Line Items] |
|
|
| Trust Preferred Securities |
$ 45,000,000 |
$ 45,000,000 |
| Subordinated debentures |
46,393,000 |
46,393,000 |
| Investment in common equity issued by Trusts |
1,400,000 |
|
| Federal Reserve Limit On Trust Preferred |
25.00% |
|
| OKSB Statutory Trust I [Member] |
|
|
| Subordinated Borrowing [Line Items] |
|
|
| Trust Preferred Securities |
20,000,000 |
20,000,000 |
| Adjustable rate |
90-day LIBOR |
|
| Adjustable rate, additional percentage |
3.10% |
|
| Amount of trust common equity sold to Southwest |
600,000 |
|
| Subordinated debentures |
20,619,000 |
20,619,000 |
| Outstanding common securities of the Trust |
619 |
|
| Trust liquidation value per share |
$ 1,000 |
|
| SBI Capital Trust II [Member] |
|
|
| Subordinated Borrowing [Line Items] |
|
|
| Trust Preferred Securities |
25,000,000 |
25,000,000 |
| Adjustable rate |
90-day LIBOR |
|
| Adjustable rate, additional percentage |
2.85% |
|
| Amount of trust common equity sold to Southwest |
800,000 |
|
| Subordinated debentures |
25,774,000 |
25,774,000 |
| Outstanding common securities of the Trust |
774 |
|
| Trust liquidation value per share |
$ 1,000 |
|
| Southwest Capital Trust II [Member] |
|
|
| Subordinated Borrowing [Line Items] |
|
|
| Trust Preferred Securities |
34,500,000 |
|
| Adjustable rate, additional percentage |
10.50% |
|
| Amount of trust common equity sold to Southwest |
1,100,000 |
|
| Amount of trust common equity redeemed by Southwest |
1,100,000 |
|
| OKSB Subordinated Debentures [Member] |
|
|
| Subordinated Borrowing [Line Items] |
|
|
| Adjustable rate |
90-day LIBOR |
|
| Adjustable rate, additional percentage |
3.10% |
|
| Principal amount of subordinated debentures |
20,600,000 |
|
| SBI II Subordinated Debentures [Member] |
|
|
| Subordinated Borrowing [Line Items] |
|
|
| Adjustable rate |
90-day LIBOR |
|
| Adjustable rate, additional percentage |
2.85% |
|
| Principal amount of subordinated debentures |
25,800,000 |
|
| OKSBP Subordinated Debentures [Member] |
|
|
| Subordinated Borrowing [Line Items] |
|
|
| Adjustable rate, additional percentage |
10.50% |
|
| Principal amount of subordinated debentures |
35,600,000 |
|
| Trust Preferred Securities [Member] |
|
|
| Subordinated Borrowing [Line Items] |
|
|
| Trust liquidation value per share |
$ 25 |
|
| Tier one capital |
$ 45,000,000 |
|