Employee Benefit Plans (Schedule of Benefit Obligation, Fair Value of Plan Assets and Funded Status) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	$ 51,112	$ 39,682
Service cost	1,227	1,315	1,169
Interest cost	2,140	2,159	2,051
Curtailments	(814)
Actuarial (gain) loss	3,590	8,480
Benefits paid	(742)	(524)
Benefit obligation, ending balance	56,513	51,112	39,682
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	35,052	34,354
Actual return on plan assets	4,013	(536)
Employer contributions	1,392	1,758
Benefits paid	(742)	(524)
Fair value of plan assets, ending balance	39,715	35,052	34,354
Funded (unfunded) status	(16,798)	(16,060)
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	86,150	73,840
Service cost	5,808	5,197	4,661
Interest cost	3,398	3,434	3,728
Actuarial (gain) loss	10,752	5,225
Benefits paid, unfunded	(1,270)	(1,546)
Benefit obligation, ending balance	104,838	86,150	73,840
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Funded (unfunded) status	$ (104,838)	$ (86,150)