Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation Plans - Outstanding Awards Under 2013 Omnibus Equity Incentive Plan (Detail)

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Stock-Based Compensation Plans - Outstanding Awards Under 2013 Omnibus Equity Incentive Plan (Detail) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 6 Months Ended
May 31, 2017
Feb. 28, 2017
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested shares, beginning balance     1,050,430
Granted 33,794 146,285 180,079
Vested     (266,469)
Transferred     0
Forfeited/canceled     (19,414)
Nonvested shares, ending balance     944,626
Unrecognized stock-based compensation expense as of June 30, 2017     $ 20,773
Weighted average remaining vesting period (years) as of June 30, 2017     3 years 18 days
Nonvested weighted average grant date fair value per share, beginning balance     $ 22.38
Weighted average grant date fair value per share, Granted     27.17
Weighted average grant date fair value, Vested     20.00
Weighted average grant date fair value, Transferred     26.63
Weighted average grant date fair value, Forfeited/canceled     23.79
Nonvested weighted average grant date fair value per share, ending balance     $ 23.93
Restricted Stock Awards [Member] | Non-Employee Directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested shares, beginning balance     29,112
Granted 13,986 0 13,986
Vested     (15,918)
Transferred     0
Forfeited/canceled     0
Nonvested shares, ending balance     27,180
Unrecognized stock-based compensation expense as of June 30, 2017     $ 663
Weighted average remaining vesting period (years) as of June 30, 2017     2 years 2 months 12 days
Restricted Stock Units [Member] | Employees [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested shares, beginning balance     566,480
Granted 8,156 139,013 147,169
Vested     (134,347)
Transferred     (24,302)
Forfeited/canceled     (19,414)
Nonvested shares, ending balance     535,586
Unrecognized stock-based compensation expense as of June 30, 2017     $ 12,183
Weighted average remaining vesting period (years) as of June 30, 2017     3 years 5 months 16 days
Restricted Stock Units [Member] | Independent Contractors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested shares, beginning balance     454,838
Granted 11,652 7,272 18,924
Vested     (116,204)
Transferred     24,302
Forfeited/canceled     0
Nonvested shares, ending balance     381,860
Unrecognized stock-based compensation expense as of June 30, 2017     $ 7,927
Weighted average remaining vesting period (years) as of June 30, 2017     2 years 6 months