Parent Company Only Financial Statements Parent Company Only Financial Statements, Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows From Operating Activities: [Abstract]
Net income	$ 232,281	$ 292,259	$ 295,479
Adjustments to reconcile net income to net cash provided by (used in) operating activities: [Abstract]
Tax effect from equity compensation, net	(1,505)	(925)	(8,258)
Change in other assets	(49,565)	(29,548)	68,821
Change in other liabilities	(11,413)	15,756	1,007
Net cash provided by operating activities	(93,454)	295,010	(36,630)
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	899,381	1,600,380	2,664,740
Acquisitions, net of cash acquired	56,017	(18,098)	(21,898)
Net cash used in investing activities	(286,007)	(2,001,304)	(434,020)
Cash Flows From Financing Activities: [Abstract]
Issuance of subordinated debentures, net of issuance costs	144,615	0	0
Issuance of common and treasury stock, net	12,455	6,711	4,472
Tax effect from equity compensation, net	1,505	925	8,258
Dividends paid	(113,455)	(115,281)	(111,026)
Repurchase of common stock	(66,792)	(229,540)	(12,337)
Net cash used in financing activities	273,359	1,874,051	1,859,279
Net decrease in cash and cash equivalents	(106,102)	167,757	1,388,629
Cash and cash equivalents at beginning of period	2,643,599	2,475,842	1,087,213
Cash and cash equivalents at end of period	2,537,497	2,643,599	2,475,842
Cash paid for interest	82,876	66,091	65,721
Issuance of shares in settlement of deferred compensation, net			8,352
Parent Company [Member]
Cash Flows From Operating Activities: [Abstract]
Net income	232,668	288,565	292,435
Adjustments to reconcile net income to net cash provided by (used in) operating activities: [Abstract]
Equity in undistributed income of bank subsidiaries	(216,120)	(134,045)	(214,435)
Equity in undistributed income of non-bank subsidiaries	21,984	(4,931)	(4,183)
Tax effect from equity compensation, net	(1,505)	(925)	(8,258)
Change in other assets	(2,933)	49	8,726
Change in other liabilities	(1,285)	(2,818)	1,055
Net cash provided by operating activities	32,809	145,895	75,340
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	1,632	4,760	0
Investment in subsidiaries	(26,000)	(41,969)	(15,336)
Acquisitions, net of cash acquired	(105,520)	0	0
Net cash used in investing activities	(129,888)	(37,209)	(15,336)
Cash Flows From Financing Activities: [Abstract]
Issuance of subordinated debentures, net of issuance costs	144,615	0	0
Issuance of common and treasury stock, net	12,455	6,711	4,472
Tax effect from equity compensation, net	1,505	925	8,258
Dividends paid	(113,455)	(115,281)	(111,026)
Repurchase of common stock	(66,792)	(229,540)	(12,337)
Net cash used in financing activities	(21,672)	(337,185)	(110,633)
Net decrease in cash and cash equivalents	(118,751)	(228,499)	(50,629)
Cash and cash equivalents at beginning of period	282,169	510,668	561,297
Cash and cash equivalents at end of period	163,418	282,169	510,668
Cash paid for interest	4,127	131	293
Issuance of shares in settlement of deferred compensation, net	$ 0	$ 0	$ 8,352