Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock-Based Compensation
Stock-based compensation expense	$ 4,000,000	$ 2,800,000	$ 3,600,000
Income tax benefit	1,500,000	1,000,000	1,300,000
Stock Options
Shares
Balance at beginning of year (in shares)	1,143,000	1,056,000	1,061,000
Granted (in shares)	156,000	190,000	142,000
Exercised (in shares)	(440,000)	(103,000)	(66,000)
Forfeited (in shares)	(1,000)
Expired (in shares)			(81,000)
Balance at end of year (in shares)	858,000	1,143,000	1,056,000
Options exercisable at end of year (in shares)	528,000	810,000	762,000
Weighted-Average Exercise Price
Balance at beginning of year (in dollars per share)	$ 11.59	$ 10.84	$ 9.58
Granted (in dollars per share)	$ 13.86	$ 11.19	$ 13.87
Exercised (in dollars per share)	$ 11.10	$ 3.20	$ 4.46
Forfeited (in dollars per share)	$ 13.87
Expired (in dollars per share)			$ 4.82
Balance at end of year (in dollars per share)	$ 12.24	$ 11.59	$ 10.84
Other information
Intrinsic value of options exercised	3,000,000	800,000	500,000
Weighted-average remaining contractual term of options exercisable	5 years 2 months 12 days
Aggregate intrinsic value of options exercisable	4,000,000
Number of options that are vested and expected to vest (in shares)	900,000
Weighted average exercise price of options that are vested and expected to vest (in dollars per share)	$ 12.24
Weighted-average remaining contractual term of options that are vested and expected to vest	6 years 6 months
Aggregate intrinsic value of options that are vested and expected to vest	$ 6,100,000