Stock-Based Compensation (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Stock-based compensation
Stock-based compensation expense recognized related to stock compensation plans	$ 3,000,000	$ 3,000,000
Additional disclosures
Proceeds from exercise of stock options	2,532,000	5,375,000
Tax benefit from exercise of stock options	854,000	3,000,000
Stock options
Stock-based compensation
Stock-based compensation expense recognized related to stock compensation plans	1,900,000	1,800,000
Stock option activity
Options outstanding at the beginning of the period (in shares)	4,273,000
Granted (in shares)	50,000
Exercised (in shares)	(262,000)	(500,000)
Forfeited (in shares)	(143,000)
Expired (in shares)	(8,000)
Options outstanding at the end of the period (in shares)	3,910,000
Options expected to vest at the end of the period (in shares)	1,832,000
Options exercisable at the end of the period (in shares)	2,035,000
Stock options, Weighted Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 17.53
Granted (in dollars per share)	$ 20.41
Exercised (in dollars per share)	$ 9.67
Forfeited (in dollars per share)	$ 23.24
Expired (in dollars per shares)	$ 26.08
Options outstanding at the end of the period (in dollars per share)	$ 17.86
Options expected to vest at the end of the period (in dollars per share)	$ 22.53
Options exercisable at the end of the period (in dollars per share)	$ 13.56
Stock options, Weighted Average Remaining Contractual Terms
Options outstanding at the end of the period	4 years 8 months 23 days
Options expected to vest at the end of the period	6 years 3 months 7 days
Options exercisable at the end of the period	3 years 3 months 7 days
Stock options, Aggregate Intrinsic Value
Options outstanding at the end of the period	16,661,000
Options expected to vest at the end of the period	1,144,000
Options exercisable at the end of the period	15,485,000
Weighted-average grant-date fair value per share of the stock options granted (in dollars per share)	$ 6.88	$ 9.72
Assumptions used to determine fair value of options granted
Risk-free interest rate (as a percent)	1.65%	0.67%
Expected volatility (as a percent)	37.08%	40.05%
Expected life	4 years 9 months 22 days	4 years 5 months 19 days
Additional disclosures
Proceeds from exercise of stock options	2,500,000	5,400,000
Tax benefit from exercise of stock options	$ 900,000	$ 3,000,000