Assets and Liabilities Measured at Fair Value - Assets and liabilities measured at fair value on nonrecurring basis (Details 2) (Nonrecurring, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Level 1
Presentation of United's assets and liabilities measured at fair value on nonrecurring basis
Loans
Foreclosed properties
Total assets
Level 2
Presentation of United's assets and liabilities measured at fair value on nonrecurring basis
Loans
Foreclosed properties
Total assets
Level 3
Presentation of United's assets and liabilities measured at fair value on nonrecurring basis
Loans	74,685	165,751	160,266
Foreclosed properties	3,802	14,788	25,253
Total assets	78,487	180,539	185,519
Total
Presentation of United's assets and liabilities measured at fair value on nonrecurring basis
Loans	74,685	165,751	160,266
Foreclosed properties	3,802	14,788	25,253
Total assets	$ 78,487	$ 180,539	$ 185,519