Employee Benefit Plans (Fair Value Of Pension Plan Assets By Asset Category) (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
U.S. government obligations		$ 727,076	$ 501,407
Government-sponsored enterprise obligations		793,023	963,127
State and municipal obligations		1,741,957	1,813,201
Agency mortgage-backed securities		2,618,281	2,593,708
Non-agency mortgage-backed securities		879,963	382,744
Asset-backed securities		2,644,381	3,091,993
Pension Plans [Member]
U.S. government obligations		2,540	1,290
Government-sponsored enterprise obligations	[1]	1,208	1,259
State and municipal obligations		10,478	10,638
Agency mortgage-backed securities	[2]	1,352	1,762
Non-agency mortgage-backed securities		5,740	5,635
Asset-backed securities		6,965	5,776
Corporate bonds	[3]	32,800	34,264
U.S. large-cap	[4]	15,746	20,296
U.S. mid-cap	[4]	12,960	13,362
U.S. small-cap	[4]	2,545	3,590
International developed markets	[4]	3,125	3,377
Emerging markets	[4]	392	473
Money market funds	[4]	3,474	3,072
Total		99,325	104,794
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
U.S. government obligations		727,076	501,407
Government-sponsored enterprise obligations		0	0
State and municipal obligations		0	0
Agency mortgage-backed securities		0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Pension Plans [Member]
U.S. government obligations		2,540	1,290
Government-sponsored enterprise obligations	[1]	0	0
State and municipal obligations		0	0
Agency mortgage-backed securities	[2]	0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Corporate bonds	[3]	0	0
U.S. large-cap	[4]	15,746	20,296
U.S. mid-cap	[4]	12,960	13,362
U.S. small-cap	[4]	2,545	3,590
International developed markets	[4]	3,125	3,377
Emerging markets	[4]	392	473
Money market funds	[4]	3,474	3,072
Total		40,782	45,460
Significant Other Observable Inputs (Level 2) [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations		793,023	963,127
State and municipal obligations		1,724,762	1,718,058
Agency mortgage-backed securities		2,618,281	2,593,708
Non-agency mortgage-backed securities		879,963	382,744
Asset-backed securities		2,644,381	3,091,993
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations	[1]	1,208	1,259
State and municipal obligations		10,478	10,638
Agency mortgage-backed securities	[2]	1,352	1,762
Non-agency mortgage-backed securities		5,740	5,635
Asset-backed securities		6,965	5,776
Corporate bonds	[3]	32,800	34,264
U.S. large-cap	[4]	0	0
U.S. mid-cap	[4]	0	0
U.S. small-cap	[4]	0	0
International developed markets	[4]	0	0
Emerging markets	[4]	0	0
Money market funds	[4]	0	0
Total		58,543	59,334
Significant Unobservable Inputs (Level 3) [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations		0	0
State and municipal obligations		17,195	95,143
Agency mortgage-backed securities		0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations	[1]	0	0
State and municipal obligations		0	0
Agency mortgage-backed securities	[2]	0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Corporate bonds	[3]	0	0
U.S. large-cap	[4]	0	0
U.S. mid-cap	[4]	0	0
U.S. small-cap	[4]	0	0
International developed markets	[4]	0	0
Emerging markets	[4]	0	0
Money market funds	[4]	0	0
Total		$ 0	$ 0

[1] This category represents bonds (excluding mortgage-backed securities) issued by agencies such as the Federal Home Loan Bank, the Federal Home Loan Mortgage Corp and the Federal National Mortgage Association.

[2] This category represents mortgage-backed securities issued by the agencies mentioned in (a).

[3] This category represents investment grade bonds issued in the U.S., primarily by domestic issuers, representing diverse industries.

[4] This category represents investments in individual common stocks and equity funds. These holdings are diversified, largely across the financial services, consumer goods, healthcare, technology, and manufacturing sectors.