Quarterly report pursuant to Section 13 or 15(d)

Selected Balance Sheet Data - Summary of Net Change in Carrying Value of Assets Held in Rabbi Trust and Deferred Compensation Obligation (Detail)

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Selected Balance Sheet Data - Summary of Net Change in Carrying Value of Assets Held in Rabbi Trust and Deferred Compensation Obligation (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Balance Sheet Related Disclosures [Abstract]        
Increase (decrease) in the carrying value of the assets held in the rabbi trust $ (104) $ 157 $ 11 $ 228
Increase (decrease) in the carrying value of the deferred compensation obligation $ (94) $ 156 $ 59 $ 233