Stock-Based Compensation (Details 5) (USD $)	12 Months Ended			0 Months Ended			1 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Feb. 11, 2013	Aug. 27, 2013	Feb. 28, 2015 item	Jan. 02, 2015	May 01, 2012	Oct. 01, 2013
Stock-Based Compensation arrangements
Stock based compensation expense	$ 21,500,000	$ 51,800,000	$ 33,500,000
Supplemental Employee Incentive Plan
Stock-Based Compensation arrangements
Stock based compensation expense	3,000,000	11,500,000	1,400,000
Number of trading days during which the closing price per share of the company's common stock equals or exceeds the goal price	20 days
Number of consecutive trading days	60 days
Period during which closing price per share equals or exceeds an interim price goal	2 years
Period during which closing price per share equals or exceeds final price goal	4 years
Percentage of the total distribution paid immediately	25.00%
Percentage of the total distribution to be deferred in accordance with the plan	75.00%
Represents the period within which total distribution will be paid.	interim or final trigger date occurs within the first 30 months from the effective date, 25% of the total distribution will be paid immediately and the remaining 75% will be deferred and paid at a future date as described in the Plan. For final trigger dates occurring during the last 18 months but before the end of the Plan, total distribution will be paid immediately.
Payments under share-based compensation plan	13,000,000	4,500,000	0
Supplemental Employee Incentive Plan | Interim trigger date
Stock-Based Compensation arrangements
Percentage of eligible employee's base salary for interim distribution	20.00%
Supplemental Employee Incentive Plan | Final trigger date
Stock-Based Compensation arrangements
Total percentage of salary eligible for final distribution if final trigger is achieved	50.00%
Incremental percentage of salary eligible for final distribution if company paid interim distributions upon achievement of the interim trigger	30.00%
SEIP II
Stock-Based Compensation arrangements
Payments under share-based compensation plan				0
SEIP III | Interim trigger date occurs by June 30, 2014
Stock-Based Compensation arrangements
Interim goal price (in dollars per share)					$ 25.00				$ 25.00
SEIP III | Interim trigger date occurs by June 30, 2014 | February 2013 Trigger Achievement
Stock-Based Compensation arrangements
Distribution to be made to company's employees due to achievement of interim goal price of $25 per share					6,800,000
Percentage of total interim distribution paid in February					25.00%
Current distribution to be made to company's employees due to achievement of interim goal price of $25 per share					1,700,000
Percentage of total interim distribution deferred					75.00%
Deferred distribution to be made to company's employees due to achievement of interim goal price of $25 per share in August 2014					4,900,000
SEIP III | Final trigger date occurs by June 30, 2016
Stock-Based Compensation arrangements
Percentage of the total distribution to be deferred in accordance with the plan						75.00%
Final goal price (in dollars per share)						$ 37.50			$ 37.50
Distribution to be made to the company's employees due to achievement of interim goal price of $25 per share						11,100,000
Percentage of the total distribution paid in September 2013						25.00%
Current distribution to be made to the company's employees due to achievement of final goal price of $37.50 per share						2,800,000
Deferred distribution to be made to the company's employees due to achievement of final goal price of $37.50 per share in August 2014						8,100,000
SEIP IV
Assumptions (as a percent)
Stock price volatility	33.40%	38.00%	39.50%
Risk free rate of return	1.00%	1.10%	0.50%
Annual salary increase rate	4.00%	4.00%	4.00%
Annual turnover rate	4.60%	4.60%	6.10%
SEIP IV | Interim trigger date occurs by September 30, 2015
Stock-Based Compensation arrangements
Interim goal price (in dollars per share)										$ 55.00
SEIP IV | Final trigger date occurs by September 30, 2017
Stock-Based Compensation arrangements
Final goal price (in dollars per share)	$ 80.00
Performance Share Awards
Stock-Based Compensation arrangements
Stock based compensation expense	20,800,000	30,900,000	24,600,000
Unamortized compensation expense	18,200,000
Unrecognized compensation expense recognition period	1 year 10 months 24 days
Aggregate intrinsic value	62,000,000
Weighted-average remaining contractual term of non-vested shares	10 months 28 days
Number of types of performance shares awards for which performance goal period ended	2
Subsequent event | Employee Performance Share Awards
Stock-Based Compensation arrangements
Number of years over which performance criteria is to be met							3 years
Number of criteria considered for awarding performance shares							3
Certified achievement, shares issuable							504,620
Certified achievement, grant date fair value of award							8,900,000
Subsequent event | TSR Performance Share Awards
Stock-Based Compensation arrangements
Certified achievement, shares issuable								234,922
Certified achievement, grant date fair value of award								3,300,000
Performance share cash award in addition to shares								$ 7,000,000