Incentive Plans and Deferred Compensation (Details) (USD $)	12 Months Ended				12 Months Ended		12 Months Ended
	Dec. 31, 2012 Long-term incentive plan	Dec. 31, 2011 Long-term incentive plan	Dec. 31, 2010 Long-term incentive plan	Dec. 31, 2012 Long-term incentive plan 2010-2012 performance period	Dec. 31, 2011 Long-term incentive plan 2009-2011 performance period	Jul. 31, 2011 Long-term incentive plan 2008-2010 performance period	Dec. 31, 2012 Long-term incentive plan Class A	Dec. 31, 2012 Annual incentive plan	Dec. 31, 2011 Annual incentive plan	Dec. 31, 2010 Annual incentive plan	Dec. 31, 2012 Deferred compensation plans	Dec. 31, 2011 Deferred compensation plans	Dec. 31, 2010 Deferred compensation plans	Dec. 31, 2012 Annual incentive, long-term incentive and deferred compensation plans	Dec. 31, 2011 Annual incentive, long-term incentive and deferred compensation plans	Dec. 31, 2010 Annual incentive, long-term incentive and deferred compensation plans	Dec. 31, 2012 Stock compensation plan for outside directors Class A	Dec. 31, 2011 Stock compensation plan for outside directors Class A	Dec. 31, 2010 Stock compensation plan for outside directors Class A
Incentive plans and deferred compensation
Performance period of incentive plans (in years)	3 years
Maximum number of shares which may be earned in each performance period by any single participant (in shares)							250,000
Maximum number of shares that may be issued pursuant to awards granted (in shares)							1,000,000
Maximum dollar amount which may be earned in each performance period by any single participant	$ 3,000,000
Estimated plan award				6,000,000
Total plan awards paid, cash based					5,000,000
Total plan awards paid, share based						5,000,000
Average share price (in dollars per share)						$ 73.97
Compensation cost charged to operations related to LTIP awards	5,000,000	9,000,000	7,000,000
Awards, employer match and hypothetical earnings by plan:
Long-term incentive plan awards	5,000,000	9,000,000	7,000,000
Annual incentive plan awards								5,000,000	3,000,000	4,000,000
Deferred compensation plans, employer match and hypothetical earnings											1,000,000	1,000,000	2,000,000
Total plan awards and earnings														11,000,000	13,000,000	13,000,000
Total plan awards paid														(8,000,000)	(10,000,000)	(6,000,000)
Compensation deferred under the plans											0	0	1,000,000
Distributions from the deferred compensation plans											(1,000,000)	(1,000,000)	(1,000,000)
Gross incentive plan and deferred compensation liabilities at end of period														26,000,000	24,000,000	22,000,000
Vesting terms under stock compensation plan for outside directors																	Each director vests in the grant 25% every three months over the course of a year.
Vesting percent under stock compensation plan for outside directors																	25.00%
Vesting period under stock compensation plan for outside directors																	3 months
Annual charge related to stock compensation plan for outside directors																	$ 500,000	$ 1,000,000	$ 2,000,000