Pensions and Postretirement Benefits Other than Pensions - Projected Benefit Obligation, Accumulated Benefit Obligation and Fair Value of Plan Assets for Pension Plans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Postretirement Benefits Other Than Pensions [Abstract]
Projected benefit obligation exceeds plan assets, Projected benefit obligation	$ 1,404,422	$ 1,438,995
Projected benefit obligation exceeds plan assets, Accumulated benefit obligation	1,401,109	1,435,193
Projected benefit obligation exceeds plan assets, Fair value of plan assets	1,112,314	1,005,574
Accumulated benefit obligation exceeds plan assets, Projected benefit obligation	1,404,422	1,438,995
Accumulated benefit obligation exceeds plan assets, Accumulated benefit obligation	1,401,109	1,435,193
Accumulated benefit obligation exceeds plan assets, Fair value of plan assets	$ 1,112,314	$ 1,005,574