Shareholders' Equity And Earnings Per Share (Components Of Other Comprehensive Income (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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	$ (7,139)	$ 12,916	(33,764)	19,037
Amount reclassified from accumulated other comprehensive loss into net income, net of tax	(967)	384	(751)	634
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	(15)	(13)	(12)	(880)
Total other comprehensive (loss) income	(8,121)	13,287	(34,527)	18,791
Balance at the end	3,106,871	2,839,458	3,106,871	2,839,458
Accumulated Unrealized Losses on Securities
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	(47,968)	(25,663)	(15,813)	(29,309)
Other comprehensive (loss) income during the period, net of tax, before reclassifications	(6,914)	10,683	(33,388)	15,162
Amount reclassified from accumulated other comprehensive loss into net income, net of tax	12	(29)	725	5
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	(15)	(13)	(12)	(880)
Total other comprehensive (loss) income	(6,917)	10,641	(32,675)	14,287
Balance at the end	(54,885)	(15,022)	(54,885)	(15,022)
Accumulated Unrealized Gains on Derivative Instruments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	10,956	5,146	7,164	4,165
Other comprehensive (loss) income during the period, net of tax, before reclassifications	1,771	(600)	4,517	165
Amount reclassified from accumulated other comprehensive loss into net income, net of tax	(979)	413	(1,476)	629
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	792	(187)	3,041	794
Balance at the end	11,748	4,959	11,748	4,959
Accumulated Foreign Currency Translation Adjustments
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	(36,083)	(39,307)	(33,186)	(40,184)
Other comprehensive (loss) income during the period, net of tax, before reclassifications	(1,996)	2,833	(4,893)	3,710
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	(1,996)	2,833	(4,893)	3,710
Balance at the end	(38,079)	(36,474)	(38,079)	(36,474)
Accumulated other comprehensive loss
Activity Accumulated Other Comprehensive Income [Roll Forward]
Balance at the beginning	(73,095)	(59,824)	(41,835)	(65,328)
Total other comprehensive (loss) income			(34,527)	18,791
Balance at the end	$ (81,216)	$ (46,537)	$ (81,216)	$ (46,537)
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)