XML 190 R176.htm IDEA: XBRL DOCUMENT v3.19.1
Note Stock-based compensation (Summary of restricted stock activity under the incentive plan for members of the Board of Directors) (Detail) - Restricted Stock Units (RSUs) - Directors - $ / shares
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Roll Forward      
Non-vested at beginning of period 0 0 0
Granted 1,052 0 25,159
Vested (1,052)   (25,159)
Forfeited 0   0
Non-vested at beginning of period 0   0
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Additional Disclosures Abstract      
Non-vested at beginning of period $ 0 $ 0 $ 0
Granted 49.25   46.71
Vested 49.25   46.71
Forfeited 0   0
Non-vested at end of period $ 0   $ 0