Maximum number of options and stock appreciation rights available per individual per calendar year.

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Maximum number of restricted shares available per individual per calendar year.

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No definition available.

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Percentage of restricted stock and restricted stock units vest.

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Share based compensation arrangement by share based payment award options grants in period grant date estimated fair value.

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No definition available.

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The total number of shares of restricted stock available for awards under the plan.

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No definition available.

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The total number of stock option awards available under the plan.

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Vesting period of awards.

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No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Amount of cash inflow from realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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-Glossary Financing Activities

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Number of share options (or share units) exercised during the current period.

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Stock Based Compensation - Additional Information (Detail) (USD $)	0 Months Ended	12 Months Ended
	May 16, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of stock, option plan, maximum	1,500,000
Aggregate number of shares issued in respect of restricted stock awards	350,000
Options available for award each plan year	1,150,000
Maximum number of shares of restricted stock or shares subject to a restricted stock units award granted		50,000
Maximum number of options and stock appreciation rights		100,000
Percentage of restricted stock and restricted stock units vest		25.00%
Vesting period of awards		1/3 per year over the first three anniversaries of the award
Recognition of compensation expense		$ 1,786,000	$ 1,908,000
Maximum term for awards granted (years)		10 years
Weighted average risk free interest rate		1.42%
Weighted average dividend yield		3.00%
Weighted average volatility factors of the expected market price of United's common stock		0.316%
Weighted-average expected option life		7 years 2 months 5 days
Estimated fair value of the options at the date of grant		$ 5.74
Total unrecognized compensation cost related to nonvested option awards		1,290,000
Weighted-average expense recognition period		10 months 24 days
Total fair value of awards vested		2,204,000
Cash received from options exercised under the plans		2,364,000	115,000	542,000
Shares issued related stock option exercises		100,302	7,510
Weighted-average grant-date fair value of options granted		$ 5.74	$ 6.86	$ 7.91
Total intrinsic value of options exercised		507,000	98,000	518,000
Excess tax benefits related to share-based compensation		331,000	35,000	3,114,000
Nonvested Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to nonvested option awards		$ 1,441,000
Weighted-average expense recognition period		1 year 6 months
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Granted		52,825
Weighted-average grant-date fair value of options granted		$ 26.19
Vesting period		4 years	4 years
Non-qualified Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Granted		194,225