Quarterly report pursuant to Section 13 or 15(d)

Equity - Summary of Unvested Shares of Restricted Common Stock (Detail)

v3.8.0.1
Equity - Summary of Unvested Shares of Restricted Common Stock (Detail) - USD ($)
$ / shares in Units, $ in Millions
9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Restricted Incentive [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Beginning Balance, Restricted Shares of Common Stock/Units 1,181,672 1,248,069
Granted, Restricted Shares of Common Stock/Units 451,614 661,055
Vested, Restricted Shares of Common Stock/Units (217,833) (716,264)
Forfeited, Restricted Shares of Common Stock/Units (4,519) (11,188)
Ending Balance, Restricted Shares of Common Stock/Units 1,410,934 1,181,672
Beginning Balance, Weighted Average Share Price $ 17.76 $ 15.16
Granted, Weighted Average Share Price 19.04 18.62
Vested, Weighted Average Share Price 14.15 14.03
Forfeited, Weighted Average Share Price 18.72 17.25
Ending Balance, Weighted Average Share Price $ 18.72 $ 17.76
Beginning Balance, Fair Value of Restricted Shares of Common Stock $ 21.0 $ 18.9
Granted, Fair Value of Restricted Shares of Common Stock 8.6 12.3
Vested, Fair Value of Restricted Shares of Common Stock (3.1) (10.0)
Forfeited, Fair Value of Restricted Shares of Common Stock (0.1) (0.2)
Ending Balance, Fair Value of Restricted Shares of Common Stock $ 26.4 $ 21.0
Restricted stock and restricted stock units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted, Restricted Shares of Common Stock/Units 256,034  
Vested, Restricted Shares of Common Stock/Units (376)  
Forfeited, Restricted Shares of Common Stock/Units (1,202)  
Ending Balance, Restricted Shares of Common Stock/Units 254,456  
Granted, Weighted Average Share Price $ 18.99  
Vested, Weighted Average Share Price 18.99  
Forfeited, Weighted Average Share Price 18.99  
Ending Balance, Weighted Average Share Price $ 18.99  
Granted, Fair Value of Restricted Shares of Common Stock $ 4.9  
Ending Balance, Fair Value of Restricted Shares of Common Stock $ 4.9