Reportable Operating Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Selected business segment financial information
Net interest income (expense)	$ 129,345	$ 117,312
Provision for loan and lease losses	(4,500)	(700)
Net interest income after provision for loan and lease losses	124,845	116,612
Noninterest income	49,407	73,519
Noninterest expense	(84,339)	(85,064)
Income before provision for income taxes	89,913	105,067
Provision for income taxes	(33,173)	(39,536)
Net income	56,740	65,531
Retail Banking
Selected business segment financial information
Net interest income (expense)	105,701	102,425
Provision for loan and lease losses	(1,663)	(256)
Net interest income after provision for loan and lease losses	104,038	102,169
Noninterest income	23,619	23,630
Noninterest expense	(55,240)	(55,136)
Income before provision for income taxes	72,417	70,663
Provision for income taxes	(26,733)	(26,988)
Net income	45,684	43,675
Commercial Banking
Selected business segment financial information
Net interest income (expense)	27,533	27,593
Provision for loan and lease losses	(2,837)	(444)
Net interest income after provision for loan and lease losses	24,696	27,149
Noninterest income	17,570	16,348
Noninterest expense	(15,049)	(11,778)
Income before provision for income taxes	27,217	31,719
Provision for income taxes	(10,034)	(12,096)
Net income	17,183	19,623
Treasury and Other
Selected business segment financial information
Net interest income (expense)	(3,889)	(12,706)
Net interest income after provision for loan and lease losses	(3,889)	(12,706)
Noninterest income	8,218	33,541
Noninterest expense	(14,050)	(18,150)
Income before provision for income taxes	(9,721)	2,685
Provision for income taxes	3,594	(452)
Net income	$ (6,127)	$ 2,233