Retirement Benefits Change in Net Benefit Obligation (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2012		Dec. 31, 2011
Qualified Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	$ 565,997		$ 532,615
Service cost	8,463		15,822
Interest cost	12,993		26,263
Actuarial loss/(gain)	2,030		18,485
Benefits paid	(20,950)		(27,188)
Medicare part D subsidiary received	0		0
Curtailment loss/(gain)	0	[1]	0	[1]
Benefit obligation at end of period	568,533		565,997
SERP Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	48,370		44,322
Service cost	537		1,241
Interest cost	1,076		2,192
Actuarial loss/(gain)	0		4,467
Benefits paid	(4,271)		(2,687)
Medicare part D subsidiary received	0		0
Curtailment loss/(gain)	0	[1]	(1,165)	[1]
Benefit obligation at end of period	45,712		48,370
Other Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	16,436		16,579
Service cost	70		113
Interest cost	375		807
Actuarial loss/(gain)	(132)		384
Benefits paid	(866)		(1,855)
Medicare part D subsidiary received	505		408
Curtailment loss/(gain)	0	[1]	0	[1]
Benefit obligation at end of period	$ 16,388		$ 16,436

[1] A curtailment gain was recognized in OCI due to the plan amendment that ceased SERP benefits for non-officers still in the plan as of December 31, 2011.