Loans Past Due Status (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Summarized details of Loans
Current	$ 22,604,417	$ 22,785,019
Nonaccrual(a)	128,939	127,901
Total loans	22,754,710	22,940,429
Nonaccrual Loans, Current Portion	$ 47,000	$ 74,000
Percent of current nonaccrual loans	36.00%	58.00%
30-59 Days Past Due
Summarized details of Loans
Total Past Due	$ 16,462	$ 21,550
60-89 Days Past Due
Summarized details of Loans
Total Past Due	2,905	3,795
90 Days or More Past Due
Summarized details of Loans
Total Past Due	$ 1,986	2,165
30-89 Days Past Due
Summarized details of Loans
Approximate Carrying Amount of Loans Sold	approximately $200,000
Commercial and industrial
Summarized details of Loans
Current	$ 7,438,395	7,356,187
Nonaccrual(a)	56,536	41,021
Total loans	7,495,623	7,398,044
Commercial and industrial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	220	187
Commercial and industrial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	206	338
Commercial and industrial | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	266	311
Commercial real estate — owner occupied
Summarized details of Loans
Current	912,810	913,787
Nonaccrual(a)	68	3,957
Total loans	915,524	920,443
Commercial real estate — owner occupied | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,646	2,580
Commercial real estate — owner occupied | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	119
Commercial real estate — owner occupied | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial and business lending
Summarized details of Loans
Current	8,351,205	8,269,974
Nonaccrual(a)	56,604	44,978
Total loans	8,411,147	8,318,487
Commercial and business lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,867	2,767
Commercial and business lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	206	457
Commercial and business lending | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	266	311
Commercial real estate — investor
Summarized details of Loans
Current	3,797,840	3,745,835
Nonaccrual(a)	4,800	1,952
Total loans	3,803,277	3,751,554
Commercial real estate — investor | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	0	2,954
Commercial real estate — investor | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	636	813
Commercial real estate — investor | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Real estate construction
Summarized details of Loans
Current	1,355,371	1,333,722
Nonaccrual(a)	542	979
Total loans	1,356,508	1,335,031
Real estate construction | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	571	330
Real estate construction | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	24	0
Real estate construction | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial real estate lending
Summarized details of Loans
Current	5,153,211	5,079,557
Nonaccrual(a)	5,342	2,931
Total loans	5,159,784	5,086,585
Commercial real estate lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	571	3,284
Commercial real estate lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	661	813
Commercial real estate lending | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Total commercial
Summarized details of Loans
Current	13,504,416	13,349,531
Nonaccrual(a)	61,946	47,909
Total loans	13,570,932	13,405,072
Total commercial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	3,438	6,051
Total commercial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	866	1,270
Total commercial | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	266	311
Residential mortgage
Summarized details of Loans
Current	7,889,681	8,200,432
Nonaccrual(a)	57,056	67,574
Total loans	$ 7,954,801	8,277,712
Approximate Carrying Amount of Loans Sold	approximately $240 million
Residential mortgage | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	$ 7,866	9,272
Residential mortgage | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	197	434
Residential mortgage | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Total consumer
Summarized details of Loans
Total loans	9,183,778	9,535,357
Carrying Amount Of Loans Sold	33,000
Home equity
Summarized details of Loans
Current	865,017	876,085
Nonaccrual(a)	9,828	12,339
Total loans	879,642	894,473
Home equity | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	3,837	4,826
Home equity | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	961	1,223
Home equity | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Other consumer
Summarized details of Loans
Current	345,303	358,970
Nonaccrual(a)	109	79
Total loans	349,335	363,171
Other consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	1,321	1,401
Other consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	881	868
Other consumer | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	1,720	1,853
Total consumer
Summarized details of Loans
Current	9,100,001	9,435,487
Nonaccrual(a)	66,993	79,992
Total loans	9,183,778	9,535,357
Total consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	13,025	15,499
Total consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	2,038	2,525
Total consumer | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	$ 1,720	$ 1,853