Shareholders' Equity And Earnings Per Share (Components Of Other Comprehensive Income (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning			$ 2,976,939	$ 2,695,617
Other comprehensive (loss) income during the period, net of tax, before reclassifications	$ (9,484)	$ 5,087	(43,248)	24,124
Amount reclassified from accumulated other comprehensive loss into net income, net of tax	(2,426)	(16)	(3,177)	618
Amount reclassified from accumulated other comprehensive loss related to amortization of unrealized losses on investment securities transferred to held-to-maturity from available-for-sale, net of tax	(24)	(20)	(36)	(900)
Total other comprehensive (loss) income	(11,934)	5,051	(46,461)	23,842
Balance at the end	3,179,822	2,908,925	3,179,822	2,908,925
Accumulated Unrealized Losses on Securities
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	(54,885)	(15,022)	(15,813)	(29,309)
Other comprehensive (loss) income during the period, net of tax, before reclassifications	(13,277)	653	(46,665)	15,815
Amount reclassified from accumulated other comprehensive loss into net income, net of tax	(730)	(24)	(5)	(19)
Amount reclassified from accumulated other comprehensive loss related to amortization of unrealized losses on investment securities transferred to held-to-maturity from available-for-sale, net of tax	(24)	(20)	(36)	(900)
Total other comprehensive (loss) income	(14,031)	609	(46,706)	14,896
Balance at the end	(68,916)	(14,413)	(68,916)	(14,413)
Accumulated Unrealized Gains on Derivative Instruments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	11,748	4,959	7,164	4,165
Other comprehensive (loss) income during the period, net of tax, before reclassifications	1,851	228	6,368	393
Amount reclassified from accumulated other comprehensive loss into net income, net of tax	(1,696)	8	(3,172)	637
Amount reclassified from accumulated other comprehensive loss related to amortization of unrealized losses on investment securities transferred to held-to-maturity from available-for-sale, net of tax	0	0	0	0
Total other comprehensive (loss) income	155	236	3,196	1,030
Balance at the end	11,903	5,195	11,903	5,195
Accumulated Foreign Currency Translation Adjustments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	(38,079)	(36,474)	(33,186)	(40,184)
Other comprehensive (loss) income during the period, net of tax, before reclassifications	1,942	4,206	(2,951)	7,916
Amount reclassified from accumulated other comprehensive loss into net income, net of tax	0	0	0	0
Amount reclassified from accumulated other comprehensive loss related to amortization of unrealized losses on investment securities transferred to held-to-maturity from available-for-sale, net of tax	0	0	0	0
Total other comprehensive (loss) income	1,942	4,206	(2,951)	7,916
Balance at the end	(36,137)	(32,268)	(36,137)	(32,268)
Accumulated other comprehensive loss
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	(81,216)	(46,537)	(41,835)	(65,328)
Total other comprehensive (loss) income			(46,461)	23,842
Balance at the end	$ (93,150)	$ (41,486)	$ (93,150)	$ (41,486)
ASU 2016-01
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					$ (1,880)
ASU 2016-01 | Accumulated Unrealized Losses on Securities
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					(1,880)
ASU 2016-01 | Accumulated Unrealized Gains on Derivative Instruments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					0
ASU 2016-01 | Accumulated Foreign Currency Translation Adjustments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					0
ASU 2016-01 | Accumulated other comprehensive loss
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					(1,880)
ASU 2018-02
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					(2,974)
ASU 2018-02 | Accumulated Unrealized Losses on Securities
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					(4,517)
ASU 2018-02 | Accumulated Unrealized Gains on Derivative Instruments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					1,543
ASU 2018-02 | Accumulated Foreign Currency Translation Adjustments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					0
ASU 2018-02 | Accumulated other comprehensive loss
Activity Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect adjustment					$ (2,974)