XML 272 R215.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Employee benefits - Funded Status of the plan (Detail) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Funded status of the plan:      
Fair value of plan assets at end of year $ 799,935 $ 685,823  
Pension Plans      
Funded status of the plan:      
Benefit obligation at end of year 852,551 754,558 $ 816,988
Fair value of plan assets at end of year 799,935 685,823 767,539
Funded status at year end (52,616) (68,735) (49,449)
OPEB Plan      
Funded status of the plan:      
Benefit obligation at end of year 168,681 153,415 170,720
Fair value of plan assets at end of year 0 0 0
Funded status at year end $ (168,681) $ (153,415) $ (170,720)