Parent Company Financial Information (Condensed Statements Of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other loans and securities									$ 1,814,600	$ 1,889,884	$ 2,049,928
Total interest income	490,017	473,407	493,233	484,748	498,257	509,000	512,588	518,877	1,941,405	2,038,722	2,188,581
Total interest expense									245,077	306,782	432,396
Net interest loss	(432,035)	(415,521)	(430,657)	(418,115)	(429,957)	(438,161)	(426,344)	(437,478)	(1,696,328)	(1,731,940)	(1,756,185)
Provision for loan losses	30,538	5,573	21,990	29,035	10,401	1,889	(10,853)	(15,664)	87,136	(14,227)	(74,532)
Net interest loss after provision for loan losses									1,783,464	1,717,713	1,681,653
Net impairment losses on investment securities	(141,733)	(9,067)	(4,217)	(10,117)	83,808	2,736	7,308	10,209	(165,134)	(104,061)	(33,683)
Other income (loss)									17,940	13,129	29,607
Total noninterest income									337,407	419,870	498,184
Salaries and employee benefits									912,918	885,661	874,293
Total noninterest expense	494,750	370,663	451,678	397,348	407,014	394,975	401,656	392,372	1,714,439	1,596,017	1,658,564
Income taxes (benefit)									142,977	193,416	198,583
Net Income (Loss) Attributable to Parent	(41,472)	111,514	83,026	110,723					263,791	349,516	323,804
Preferred stock dividends	(17,965)	(27,507)	(27,641)	(22,399)	(22,647)	(47,529)	(36,522)	(64,187)	95,512	170,885	170,414
Net earnings applicable to common shareholders	(59,437)	209,707	55,385	88,324	35,605	62,322	55,215	25,489	293,979	178,631	153,390
Parent Company [Member]
Commercial bank subsidiaries									757	836	2,519
Other subsidiaries and affiliates									105	386	63
Other loans and securities									17,764	18,993	13,640
Total interest income									18,626	20,215	16,222
Affiliated trusts									8,483	24,053	24,027
Other borrowed funds									171,304	195,195	274,843
Total interest expense									179,787	219,248	298,870
Net interest loss									161,161	199,033	282,648
Provision for loan losses									23	10	38
Net interest loss after provision for loan losses									(161,138)	(199,023)	(282,610)
Equity and fixed income securities gains (losses), net									(7,332)	86	426
Net impairment losses on investment securities									95,637	74,153	26,810
Other income (loss)									(8,397)	(6,562)	4,203
Total noninterest income									310,240	221,417	63,320
Salaries and employee benefits									26,014	20,507	19,033
Extinguishment of Debt, Amount									120,192	0	0
Other operating expenses									1,436	395	4,176
Total noninterest expense									147,642	20,902	23,209
Income (loss) before income taxes and undistributed income (loss) of consolidated subsidiaries									1,460	1,492	(242,499)
Income taxes (benefit)									(133,798)	(108,541)	(104,395)
Income before equity in undistributed income (loss) of consolidated subsidiaries									135,258	110,033	(138,104)
Net Income (Loss) Attributable to Parent									263,791	349,516	323,804
Preferred stock dividends									(95,512)	(170,885)	(170,414)
Preferred stock redemption									125,700	0	0
Net earnings applicable to common shareholders									293,979	178,631	153,390
Parent Company [Member] | Nonoperating - ZMFU II, Inc. [Member]
Dividends from consolidated subsidiaries									0	50,000	0
Equity in undistributed income (loss) of consolidated subsidiaries									514	(49,515)	789
Parent Company [Member] | Other Operating Companies [Member]
Dividends from consolidated subsidiaries									200	5,440	14,151
Equity in undistributed income (loss) of consolidated subsidiaries									(4,887)	(15,561)	(27,687)
Parent Company [Member] | Commercial Banks And Bank Holding Company [Member]
Dividends from consolidated subsidiaries									421,406	246,606	71,350
Equity in undistributed income (loss) of consolidated subsidiaries									$ 132,906	$ 304,559	$ 488,806