Note Employee benefits (Accumulated benefit obligation in excess of plan assets) (Detail) - USD ($) $ in Thousands |
Dec. 31, 2015 |
Dec. 31, 2014 |
---|---|---|
Pension Plan | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Projected benefit obligation | $ 736,140 | $ 777,815 |
Accumulated benefit obligation | 736,140 | 777,815 |
Fair value of plan assets | 612,283 | 662,765 |
Benefit Restoration Plans | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Projected benefit obligation | 40,773 | 42,664 |
Accumulated benefit obligation | 40,773 | 42,664 |
Fair value of plan assets | $ 32,131 | $ 34,475 |