XML 154 R126.htm IDEA: XBRL DOCUMENT v3.6.0.2
Employee Benefit Plans - Summary of Company's Performance Units Activity (Detail) - Performance Shares [Member]
12 Months Ended
Dec. 31, 2016
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of Units Non-vested Beginning Balance | shares 49,667
Number of Units Granted | shares 119,839
Number of Units Additional goal achievement shares | shares 12,727
Number of Units Vested | shares (59,830)
Number of Units Canceled | shares (122,403)
Number of Units Non-vested Ending Balance | shares  
Weighted Average Grant-Date Fair Value Non-vested Beginning Balance | $ / shares $ 64.93
Weighted Average Grant-Date Fair Value Granted | $ / shares 64.67
Weighted Average Grant-Date Fair Value Additional goal achievement shares | $ / shares 64.93
Weighted Average Grant-Date Fair Value Vested | $ / shares 64.79
Weighted Average Grant-Date Fair Value Canceled | $ / shares 64.74
Weighted Average Grant-Date Fair Value Non-vested Ending Balance | $ / shares $ 64.93