Annual report pursuant to Section 13 and 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
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Nonvested shares at beginning 891,575 981,855
Granted 355,130 258,078
Vested (400,616) (333,724)
Transferred 0 0
Forfeited/canceled (46,014) (14,634)
Nonvested shares at ending 800,075 891,575
Unrecognized stock-based compensation expense as of December 31, 2019 $ 22,014  
Weighted average remaining vesting period (years) as of December 31, 2019 3 years 5 months 23 days  
Nonvested weighted average grant date fair value per share, beginning balance $ 27.59 $ 23.90
Weighted average grant date fair value per share, Granted 38.51 34.94
Weighted average grant date fair value per share, Vested 24.29 22.31
Weighted average grant date fair value per share, Transferred 29.68 30.69
Weighted average grant date fair value per share, Forfeited/canceled 30.65 30.17
Nonvested weighted average grant date fair value per share, ending balance $ 33.91 $ 27.59
Restricted Stock Awards [Member] | Non-Employee Directors [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Nonvested shares at beginning 27,096 30,732
Granted 12,806 12,852
Vested (22,422) (16,488)
Transferred 0 0
Forfeited/canceled 0 0
Nonvested shares at ending 17,480 27,096
Unrecognized stock-based compensation expense as of December 31, 2019 $ 234  
Weighted average remaining vesting period (years) as of December 31, 2019 4 months 20 days  
Restricted Stock Units [Member] | Employees [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Nonvested shares at beginning 471,782 500,859
Granted 260,274 142,760
Vested (186,311) (146,122)
Transferred (8,136) (23,755)
Forfeited/canceled (12,494) (1,960)
Nonvested shares at ending 525,115 471,782
Unrecognized stock-based compensation expense as of December 31, 2019 $ 13,959  
Weighted average remaining vesting period (years) as of December 31, 2019 3 years 7 months 9 days  
Restricted Stock Units [Member] | Independent Contractors [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Nonvested shares at beginning 392,697 450,264
Granted 82,050 102,466
Vested (191,883) (171,114)
Transferred 8,136 23,755
Forfeited/canceled (33,520) (12,674)
Nonvested shares at ending 257,480 392,697
Unrecognized stock-based compensation expense as of December 31, 2019 $ 7,821  
Weighted average remaining vesting period (years) as of December 31, 2019 3 years 4 months 2 days