Pension and Other Postretirement Benefits - Change in Plan Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Change in plan assets:
Fair value of plan assets, end of year	$ 216,754	$ 198,367
Pension Benefits [Member]
Change in plan assets:
Fair value of plan assets, beginning of year	198,367	173,154
Actual return on plan assets	20,223	29,416
Employer contributions	7,992	10,035
Plan participant contributions	109	105
Acquisitions	9,360	0
Foreign currency exchange rate changes	(4,707)	(186)
Benefits paid	(14,590)	(14,157)
Fair value of plan assets, end of year	216,754	198,367
Funded status, end of year	(83,585)	(60,056)
Other Benefits [Member]
Change in plan assets:
Fair value of plan assets, beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	2,045	2,416
Plan participant contributions	7	11
Acquisitions	0	0
Foreign currency exchange rate changes	0	0
Benefits paid	(2,052)	(2,427)
Fair value of plan assets, end of year	0	0
Funded status, end of year	$ (39,169)	$ (46,614)