Stock-Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Stock-based compensation
Stock-based compensation expense recognized related to stock compensation plans	$ 2,900,000	$ 2,600,000	$ 9,100,000	$ 8,700,000
Excess tax benefit from stock-based compensation			870,000	5,154,000
Assumptions used to determine fair value of options granted
Weighted-average grant-date fair value per share of the stock options granted			$ 7.24	$ 7.27
Expected life			4 years 9 months 22 days	4 years 5 months 19 days
Additional disclosures
Proceeds from exercise of stock options			3,279,000	7,381,000
Tax benefit from exercise of stock options			870,000	5,200,000
Employee Stock Option [Member]
Stock-based compensation
Stock-based compensation expense recognized related to stock compensation plans	1,700,000	1,300,000	5,300,000	4,900,000
Stock option activity
Options outstanding at the beginning of the period (in shares)			4,273,000
Granted (in shares)			193,000
Exercised (in shares)	(36,016)	(200,000)	(297,000)	(900,000)
Forfeitures (in shares)			(254,000)
Expired (in shares)			(167,000)
Options outstanding at the end of the period (in shares)	3,748,000		3,748,000		4,273,000
Options expected to vest at the end of the period (in shares)	1,796,000		1,796,000
Options exercisable at the end of the period (in shares)	1,910,000		1,910,000
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)			$ 20.17
Exercised (in dollars per share)			$ 9.31
Forfeitures (in dollars per share)			$ 23.40
Expired (in dollars per shares)			$ 22.27
Options outstanding at the end of the period (in dollars per share)	$ 17.78		$ 17.78		$ 17.53
Options expected to vest at the end of the period (in dollars per share)	$ 22.72		$ 22.72
Options exercisable at the end of the period (in dollars per share)	$ 13.02		$ 13.02
Stock options, Weighted Average Remaining Contractual Terms
Options outstanding at the end of the period	4 years 3 months 22 days				4 years 10 months 10 days
Options expected to vest at the end of the period	5 years 10 months 10 days
Options exercisable at the end of the period	2 years 9 months 26 days
Stock options, Aggregate Intrinsic Value
Options outstanding at the end of the period	15,613,000		15,613,000		27,099,000
Options expected to vest at the end of the period	402,000		402,000
Options exercisable at the end of the period	15,198,000		15,198,000
Assumptions used to determine fair value of options granted
Risk-free interest rate (as a percent)			1.56%	0.67%
Expected volatility (as a percent)			38.11%	40.05%
Expected life			4 years 9 months 22 days	4 years 5 months 19 days
Additional disclosures
Proceeds from exercise of stock options	100,000	1,100,000	3,300,000	7,400,000
Tax benefit from exercise of stock options	17,000	900,000	900,000	5,200,000
Unrecognized stock-based compensation	9,900,000		9,900,000
Weighted-average period over which compensation will be recognized			1 year 2 months 12 days
Total intrinsic value of options exercised	600,000	3,100,000	3,900,000	17,000,000
Restricted Stock Units R S U [Member]
Stock-based compensation
Stock-based compensation expense recognized related to stock compensation plans	1,200,000	1,200,000	3,700,000	3,300,000
Stock options, Aggregate Intrinsic Value
Options outstanding at the end of the period					14,429,000
Additional disclosures
Unrecognized stock-based compensation	10,000,000		10,000,000
Weighted-average period over which compensation will be recognized			1 year 6 months
Restricted Stock [Member]
Stock-based compensation
Stock-based compensation expense recognized related to stock compensation plans	$ 100,000		$ 100,000	$ 500,000