Pension and Other Employee Benefits - Schedule Fair Value of Pension Plan Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	$ 18,037	$ 25,153
Level 1 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total fixed income	10,379	13,110
U.S. government [Member] | Level 1 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total fixed income	2,915	3,849
Investment grade [Member] | Level 1 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total fixed income	5,308	6,239
Investment grade [Member] | Level 2 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	7,336	11,560
High yield [Member] | Level 1 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total fixed income	2,156	3,022
Other [Member] | Level 2 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	108	222
Cash and cash equivalents [Member] | Level 1 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	$ 214	$ 261