Employee Benefit Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Share-Based Compensation Plans
Common stock, shares, issued	403,800,000	416,200,000
Outstanding stock options, restricted stock units, and restricted stock awards from awards assumed	3,300,000
Number of Shares
Balance as of December 31, 2014 (in shares)	9,900,000
Canceled (in shares)	(100,000)
Exercised (in shares)	(300,000)
Expired (in shares)	(1,700,000)
Balance as of March 31, 2015 (in shares)	7,800,000
Weighted Average Exercise Price per Share
Balance as of December 31, 2014 (in dollars per share)	$ 24.87
Canceled (in dollars per share)	$ 23.52
Exercised (in dollars per share)	$ 14.20
Expired (in dollars per share)	$ 26.32
Balance as of March 31, 2015 (in dollars per share)	$ 25.05
Weighted average remaining contractual term at March 31, 2015	2 years 1 month 6 days
Aggregate intrinsic value at March 31, 2015	$ 22,300,000
Vested or expected-to-vest options at March 31, 2015 (in shares)	7,800,000
Vested or expected-to-vest options, weighted average exercise price at March 31, 2015 (in dollars per share)	$ 25.17
Vested and expected-to-vest options, weighted average remaining contractual term at March 31, 2015	2 years 1 month 6 days
Vested or expected-to-vest options, aggregate intrinsic value at March 31, 2015	21,500,000
Exercisable options at March 31, 2015 (in shares)	7,300,000
Exercisable options, weighted average exercise price at March 31, 2015 (in dollars per share)	$ 26.23
Exercisable options, weighted average remaining contractual term at March 31, 2015	1 year 9 months 18 days
Exercisable options, aggregate intrinsic value at March 31, 2015	14,700,000
Share price (in dollars per share)	$ 22.58
Pre-tax intrinsic value of options exercised	3,300,000
Equity incentive plan 2006
Share-Based Compensation Plans
Number of shares in authorized	149,500,000.0
Number of shares available for future issuance	36,200,000
Plan 1996 and 2000 [Member]
Share-Based Compensation Plans
Maximum additional shares expire unexercised, under 1996 and 2000 plan	75,000,000.0
Equity Incentive Plan 1996, 2000, and 2006 [Member]
Share-Based Compensation Plans
Number of shares outstanding	27,800,000
Employee stock purchase plan 2008 [Member]
Share-Based Compensation Plans
Number of shares available for future issuance	1,900,000
Common stock, capital shares reserved for future issuance	19,000,000
Share-based compensation arrangement by share-based payment award, discount from market price	15.00%
Periodic payroll deduction - percentage of base salary	10.00%
Maximum purchase of common stock, shares	6,000
Share-based compensation arrangement by share-based payment award, offering period	12 months
Maximum purchase of common stock, value	$ 25,000
Share-based compensation arrangement by share-based payment award, expiration period	1 year
Common stock, shares, issued	17,100,000