Share-Based Compensation - Activity in Company's Plan - Long Term Incentive Plan (Detail) (Long Term Incentive Plan Stock Option [Member], USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013
Long Term Incentive Plan Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at January 1, 2014, Number of Shares	17,000
Granted, Number of Shares	17,000	0
Exercised, Number of Shares	(1,250)	(9,250)
Forfeited, Number of Shares	0
Outstanding (vested and expected to vest) at June 30, 2014, Number of Shares	32,750
Exercisable at June 30, 2014, Number of Shares	11,375
Outstanding at January 1, 2014, Weighted Average Exercise Price per Share	$ 54.20
Granted, Weighted Average Exercise Price per Share	$ 71.62
Exercised, Weighted Average Exercise Price per Share	$ 52.10
Forfeited, Weighted Average Exercise Price per Share	$ 0.00
Outstanding (vested and expected to vest) at June 30, 2014, Weighted Average Exercise Price per Share	$ 63.32
Exercisable at June 30, 2014, Weighted Average Exercise Price per Share	$ 54.30
Outstanding (vested and expected to vest) at June 30, 2014, Weighted Average Remaining Contractual Term	8 years 7 months 6 days
Exercisable at June 30, 2014, Weighted Average Remaining Contractual Term	7 years 7 months 6 days
Outstanding (vested and expected to vest) at June 30, 2014, Aggregate Intrinsic Value	$ 15
Exercisable at June 30, 2014, Aggregate Intrinsic Value	$ 11

Share-Based Compensation - Activity in Company's Plan - Long Term Incentive Plan (Detail) (Long Term Incentive Plan Stock Option [Member], USD $)
In Thousands, except Share data, unless otherwise specified

6 Months Ended

Jun. 30, 2014

Jun. 30, 2013

Long Term Incentive Plan Stock Option [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Outstanding at January 1, 2014, Number of Shares

17,000

Granted, Number of Shares

17,000

Exercised, Number of Shares

(1,250)

(9,250)

Forfeited, Number of Shares

Outstanding (vested and expected to vest) at June 30, 2014, Number of Shares

32,750

Exercisable at June 30, 2014, Number of Shares

11,375

Outstanding at January 1, 2014, Weighted Average Exercise Price per Share

$ 54.20

Granted, Weighted Average Exercise Price per Share

$ 71.62

Exercised, Weighted Average Exercise Price per Share

$ 52.10

Forfeited, Weighted Average Exercise Price per Share

$ 0.00

Outstanding (vested and expected to vest) at June 30, 2014, Weighted Average Exercise Price per Share

$ 63.32

Exercisable at June 30, 2014, Weighted Average Exercise Price per Share

$ 54.30

Outstanding (vested and expected to vest) at June 30, 2014, Weighted Average Remaining Contractual Term

8 years 7 months 6 days

Exercisable at June 30, 2014, Weighted Average Remaining Contractual Term

7 years 7 months 6 days

Outstanding (vested and expected to vest) at June 30, 2014, Aggregate Intrinsic Value

$ 15

Exercisable at June 30, 2014, Aggregate Intrinsic Value

$ 11

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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