Stock-Based Compensation (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock-Based Compensation
Stock-based compensation expense recognized related to stock compensation plans	$ 3,200,000	$ 2,900,000
Assumptions used to determine fair value of options granted
Weighted-average grant-date fair value per share of the stock options granted	$ 5.89	$ 6.88
Additional disclosures
Proceeds from exercise of stock options	3,273,000	2,532,000
Tax benefit from exercise of stock options	1,448,000
Stock options
Stock-Based Compensation
Stock-based compensation expense recognized related to stock compensation plans	1,400,000	1,900,000
Stock option activity
Options outstanding at the beginning of the period (in shares)	4,101,000
Granted (in shares)	1,088,000
Exercised (in shares)	(443,000)	(300,000)
Forfeitures (in shares)	(295,000)
Expired (in shares)	(25,000)
Options outstanding at the end of the period (in shares)	4,426,000
Options expected to vest at the end of the period (in shares)	2,499,000
Options exercisable at the end of the period (in shares)	1,871,000
Stock options, Weighted Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 18.72
Granted (in dollars per share)	$ 16.77
Exercised (in dollars per share)	$ 7.40
Forfeitures (in dollars per share)	$ 23.03
Expired (in dollars per shares)	$ 24.48
Options outstanding at the end of the period (in dollars per share)	$ 19.06
Options expected to vest at the end of the period (in dollars per share)	$ 19.78
Options exercisable at the end of the period (in dollars per share)	$ 18.06
Stock options, Weighted Average Remaining Contractual Terms
Options outstanding at the end of the period	5 years 1 month 13 days
Options expected to vest at the end of the period	6 years 4 months 10 days
Options exercisable at the end of the period	3 years 5 months 1 day
Stock options, Aggregate Intrinsic Value
Options outstanding at the end of the period	5,959,000
Options expected to vest at the end of the period	4,000
Options exercisable at the end of the period	5,955,000
Assumptions used to determine fair value of options granted
Risk-free interest rate (as a percent)	1.44%	1.65%
Expected volatility (as a percent)	38.29%	37.08%
Expected life	4 years 10 months 17 days	4 years 9 months 22 days
Additional disclosures
Proceeds from exercise of stock options	3,300,000	2,500,000
Tax benefit from exercise of stock options	1,400,000	900,000
Unrecognized stock-based compensation, stock options	14,500,000
Weighted-average period over which compensation will be recognized	1 year 6 months 29 days
Total intrinsic value of options exercised	5,400,000	3,000,000
Restricted Stock Units
Stock-Based Compensation
Stock-based compensation expense recognized related to stock compensation plans	1,800,000	1,000,000
Additional disclosures
Unrecognized stock-based compensation, restricted stock	20,800,000
Weighted-average period over which compensation will be recognized	1 year 8 months 27 days
Restricted Stock
Stock-Based Compensation
Stock-based compensation expense recognized related to stock compensation plans	$ 0	$ 100,000