Comprehensive Income - Summary of (Gains) Losses Reclassified from AOCI into Condensed Consolidated Statements of Income and Affected Financial Statement Line Item (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before income taxes	$ 3,591	$ 5,092	$ 9,932	$ 10,584
Income tax benefit	650	1,590	2,431	3,246
Total net of income taxes	2,941	3,502	7,501	7,338
Amortization of actuarial losses	223	232	432	455
Total before income taxes	223	232	432	455
Income tax benefit	78	85	151	168
Total net of income taxes	145	147	281	287
Interest Rate Swaps [Member] | Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before income taxes		3,090	3,100	6,103
Foreign Exchange Forward Contracts [Member] | Service Revenues [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before income taxes	$ 3,591	$ 2,002	$ 6,832	$ 4,481