Employee Benefit Plans (Fair Value Of Pension Plan Assets By Asset Category) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
U.S. government obligations	$ 364,665		$ 455,537
Government-sponsored enterprise obligations	315,698		201,895
State and municipal obligations	1,245,284		1,119,485
Agency mortgage-backed securities	4,106,059		2,491,199
Non-agency mortgage-backed securities	316,902		455,790
Asset-backed securities	2,693,143		2,354,260
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
U.S. government obligations	357,155		448,087
Government-sponsored enterprise obligations
State and municipal obligations
Agency mortgage-backed securities
Non-agency mortgage-backed securities
Asset-backed securities
Significant Other Observable Inputs (Level 2) [Member]
U.S. government obligations	7,510		7,450
Government-sponsored enterprise obligations	315,698		201,895
State and municipal obligations	1,109,663		969,396
Agency mortgage-backed securities	4,106,059		2,491,199
Non-agency mortgage-backed securities	316,902		455,790
Asset-backed securities	2,693,143		2,354,260
Significant Unobservable Inputs (Level 3) [Member]
State and municipal obligations	135,621		150,089
Pension Plans [Member]
Cash	164		22
U.S. government obligations	4,863		3,964
Government-sponsored enterprise obligations	9,749	[1]	9,771	[1]
State and municipal obligations	5,005		3,644
Agency mortgage-backed securities	4,480	[2]	5,848	[2]
Non-agency mortgage-backed securities	6,908		7,802
Asset-backed securities	8,085		6,060
Corporate bonds	22,700	[3]	19,676	[3]
International bonds	3,169		2,274
U.S. large-cap	13,928	[4]	17,806	[4]
U.S. mid-cap	8,250	[4]	8,849	[4]
U.S. small-cap	3,348	[4]	3,344	[4]
International developed markets	1,184	[4]	1,951	[4]
Emerging markets	1,569	[4]	2,771	[4]
Money market funds	3,826	[4]	5,042	[4]
Total	97,228		98,824
Pension Plans [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Cash	164		22
U.S. government obligations	4,863		3,964
U.S. large-cap	13,928	[4]	17,806	[4]
U.S. mid-cap	8,250	[4]	8,849	[4]
U.S. small-cap	3,348	[4]	3,344	[4]
International developed markets	1,184	[4]	1,951	[4]
Emerging markets	1,569	[4]	2,771	[4]
Money market funds	3,826	[4]	5,042	[4]
Total	37,132		43,749
Pension Plans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Government-sponsored enterprise obligations	9,749	[1]	9,771	[1]
State and municipal obligations	5,005		3,644
Agency mortgage-backed securities	4,480	[2]	5,848	[2]
Non-agency mortgage-backed securities	6,908		7,802
Asset-backed securities	8,085		6,060
Corporate bonds	22,700	[3]	19,676	[3]
International bonds	3,169		2,274
Total	60,096		55,075
Pension Plans [Member] | Significant Unobservable Inputs (Level 3) [Member]
Cash
U.S. government obligations
Government-sponsored enterprise obligations		[1]		[1]
State and municipal obligations
Agency mortgage-backed securities		[2]		[2]
Non-agency mortgage-backed securities
Asset-backed securities
Corporate bonds		[3]		[3]
International bonds
U.S. large-cap		[4]		[4]
U.S. mid-cap		[4]		[4]
U.S. small-cap		[4]		[4]
International developed markets		[4]		[4]
Emerging markets		[4]		[4]
Money market funds		[4]		[4]
Total

[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 of U.S. issuers from diverse industries.

[4] This category represents investments in individual common stocks and equity funds. The majority of these investments are in equity mutual funds, which have diversified investment holdings as of December 31, 2011 across the financial services, industrial materials, technology, consumer goods, healthcare, and energy sectors.