Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified to Net Income from Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax amount	$ 17,591	$ 9,713	$ 39,030	$ 24,586
Tax (provision) benefit	4,679	1,376	10,479	5,936
Reclassification of gain (loss) to net income	12,912	8,337	28,551	18,650
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of gain (loss) to net income	769	(1,714)	1,390	(3,972)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Actuarial Gain (Loss) Related to Pension Liability [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of gain (loss) to net income	10	13	21	25
Reclassification out of Accumulated Other Comprehensive Income [Member] | Gain (Loss) on Cash Flow Hedging Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax (provision) benefit	5	17	11	113
Reclassification of gain (loss) to net income	745	(1,739)	1,341	(4,020)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Gain (Loss) on Post Retirement Obligation [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of gain (loss) to net income	14	12	28	23
Reclassification out of Accumulated Other Comprehensive Income [Member] | Direct Salaries and Related Costs [Member] | Actuarial Gain (Loss) Related to Pension Liability [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax amount	10	13	21	25
Reclassification out of Accumulated Other Comprehensive Income [Member] | Revenues [Member] | Gain (Loss) on Cash Flow Hedging Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax amount	740	(1,756)	1,330	(4,133)
Reclassification out of Accumulated Other Comprehensive Income [Member] | General and Administrative [Member] | Gain (Loss) on Post Retirement Obligation [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax amount	$ 14	$ 12	$ 28	$ 23