Accumulated Other Comprehensive Loss, Net of Tax (Schedule of Accumulated Other Comprehensive Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Impairment loss recognized in earnings	$ 0	$ (73)	$ 0	$ (161)
Income tax expense	(20,663)	(23,159)	(44,755)	(44,396)
Interest expense	(23,459)	(22,375)	(46,607)	(44,853)
Compensation and benefits	74,043	65,711	144,907	132,082
Net income	52,503	47,834	102,225	98,263
Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Impairment loss recognized in earnings			0	(161)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investment securities	486	0	529	4,336
Impairment loss recognized in earnings	0	(73)
Income tax expense	(177)	26	(193)	(1,495)
Net income	309	(47)	336	2,680
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	803	757	1,567	1,553
Interest expense	(2,192)	(2,115)	(4,284)	(4,336)
Net income	(1,389)	(1,358)	(2,717)	(2,783)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Compensation and benefits	(734)	26	(1,406)	52
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Compensation and benefits	(18)	(18)	(36)	(36)
Defined benefit pension and postretirement benefit plans [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	276	(3)	528	(6)
Net income	$ (476)	$ 5	$ (914)	$ 10