Summary of Retirement Plan Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Employee Benefit Plans [Line Items]
Retirement plan expense	$ 68,244	$ 85,984	$ 81,210
Defined contribution retirement plans
Schedule of Employee Benefit Plans [Line Items]
Retirement plan expense	43,819	43,694	40,266
Defined benefit pension plans
Schedule of Employee Benefit Plans [Line Items]
Retirement plan expense	18,124	30,747	33,597
Deferred compensation and excess benefit plans
Schedule of Employee Benefit Plans [Line Items]
Retirement plan expense	4,840	9,298	5,740
Postretirement benefit plans
Schedule of Employee Benefit Plans [Line Items]
Retirement plan expense	$ 1,461	$ 2,245	$ 1,607

- Definition

The amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss) on assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period is the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost is accrued during the employee's service period).

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