XML 120 R102.htm IDEA: XBRL DOCUMENT v3.8.0.1
Subsequent Events - Additional Information (Detail) - $ / shares
3 Months Ended 12 Months Ended
Jan. 22, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Subsequent Event [Line Items]                                
Cash dividend declared per common share   $ 0.27 $ 0.14 $ 0.14 $ 0.14 $ 0.27 $ 0.14 $ 0.14 $ 0.14 $ 0.27 $ 0.12 $ 0.12 $ 0.12 $ 0.69 $ 0.69 $ 0.63
Subsequent Event [Member]                                
Subsequent Event [Line Items]                                
Dividend declared date Jan. 22, 2018                              
Cash dividend declared per common share $ 0.14                              
Dividend payable date Mar. 12, 2018                              
Dividends payable, shareholders record date Feb. 28, 2018