Stock Compensation Plans and Other Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended					12 Months Ended					12 Months Ended					12 Months Ended				12 Months Ended							12 Months Ended
	Dec. 31, 2012 employees	Dec. 31, 2011	Dec. 31, 2010	Dec. 12, 2012	May 31, 2012	Dec. 31, 2012 2007 Plan [Member]	Dec. 31, 2011 2007 Plan [Member]	Dec. 31, 2010 2007 Plan [Member]	May 31, 2011 2007 Plan [Member]	May 31, 2009 2007 Plan [Member]	Dec. 31, 2012 1997 Plan [Member]	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2009 Restricted Stock [Member]	Dec. 31, 2012 Long-Term Incentive Program Awards [Member]	Dec. 31, 2012 Performance Shares [Member]	Dec. 31, 2011 Performance Shares [Member]	Dec. 31, 2010 Performance Shares [Member]	Dec. 31, 2012 Cash Incentive And Retention Plan (CIRP) [Member]	Dec. 31, 2011 Cash Incentive And Retention Plan (CIRP) [Member]	Dec. 31, 2010 Cash Incentive And Retention Plan (CIRP) [Member]	Dec. 31, 2012 Directors Deferred Fee And Stock Plan (DDFS Plan) [Member]	Dec. 31, 2011 Directors Deferred Fee And Stock Plan (DDFS Plan) [Member]	Dec. 31, 2010 Directors Deferred Fee And Stock Plan (DDFS Plan) [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Minimum [Member] 2007 Plan [Member]	Dec. 31, 2012 Minimum [Member] Restricted Stock [Member]	Dec. 31, 2012 Minimum [Member] Long-Term Incentive Program Awards [Member]	Dec. 31, 2012 Maximum [Member] 2007 Plan [Member]	Dec. 31, 2012 Maximum [Member] Restricted Stock [Member]	Dec. 31, 2012 Maximum [Member] Long-Term Incentive Program Awards [Member]	Dec. 31, 2012 Maximum [Member] Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved for issuance						500,000																	242,540
Shares additionally approved for issuance									2,860,000	325,000
Shares available for future grants						1,339,252																	105,812
Award vesting period, minimum, years																3 years											3 years	1 year		5 years	5 years
Share based payment award options term						7 years					10 years					7 years
Percentage of performance based award payouts																													0.00%			200.00%
Compensation cost charged to income for stock options	$ 9,100,000	$ 5,600,000	$ 4,400,000
Tax benefit from stock options exercised	3,300,000	2,200,000	1,700,000
Weighted average per share grant date fair value (in usd per share)	$ 15.00	$ 15.84	$ 15.83
Aggregate intrinsic value of options exercised	5,400,000	1,200,000	3,200,000
Cash received from options exercises under the plans	10,400,000	1,500,000	2,400,000
Tax benefit realized for the tax deductions from option exercised	2,100,000	468,000	1,200,000									15,000	(72,000)	(28,000)
Maximum number of shares that could be issued based on the grants made to date												314,226	336,709	299,040	208,430		153,915	72,158	0														429,000
Weighted average grant date fair value per share of options granted (in usd per share)							$ 32.59	$ 33.15				$ 32.37	$ 32.85	$ 35.20			$ 31.10	$ 33.25
Shares granted to certain executives							446	5,279				111,207	98,394	149,656			119,476	100,993
Unrecognized compensation cost related to non-vested share based arrangements	10,900,000
Nonvested awards, total compensation cost not yet recognized, period for recognition, years	2 years
Total fair value of shares vested	6,400,000	4,100,000	9,500,000
Company's expense																				357,000	295,000	368,000
Payment of vested awards												1,200,000
Employee requisite service period	501 hours
Company's expense for the employer contributions	4,300,000	4,000,000	3,600,000
Rate of purchase price of the shares of common stock																										85.00%
Stock options purchase price calculation at fair value, percentage	90.00%
Number of shares earned by the participants under the SPP	66,237	71,077	53,909
Compensation expense recognized under the SPP	421,000	300,000	274,000
Authorized additional shares of common stock under the SPP					300,000
Number of shares the company is obligated to issue to participants under the SPP	12,969
Number of shares available for future grants under the SPP	321,116
Number of employees covered by pension plan	100
Net liability recorded related to the HPK Plan				2,000,000
Accumulated benefit obligation related to the HPK Plan	7,900,000
Fair value of HPK Plan's assets	5,600,000
Discount rate used related with the HPK Plan	3.98%
Estimated future contribution to the HPK Plan for 2013	67,000
Expected future benefit payments by the HPK Plan in 2013	$ 614,000
Shares issued																							22,220	25,242	47,830