Share-Based Compensation Plans (Details) (USD $) Share data in Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	$ 5,457,000	$ 4,662,000	$ 15,446,000	$ 14,264,000
Income tax benefit	(1,864,000)	(1,549,000)	(5,253,000)	(4,876,000)
Share-based compensation expense, net of tax	3,593,000	3,113,000	10,193,000	9,388,000
Summary of compensation expense recognized related to cash awards
Cash awards	389,000	934,000	1,655,000	3,101,000
Share Based Compensation Plans (Textuals) [Abstract]
Total awards granted			642	583
Total unrecognized pre-tax compensation expense	30,500,000		30,500,000
Unrecognized Compensation Costs weighted-average period (in years)			1 year 10 months 24 days
Stock Option [Member]
Share Based Compensation Plans (Textuals) [Abstract]
Stock option plan granted			406	391
Market-based restricted stock rights [Member]
Share Based Compensation Plans (Textuals) [Abstract]
Restricted stock rights and restricted stock units granted			22	23
Performance based restricted stock [Member]
Share Based Compensation Plans (Textuals) [Abstract]
Restricted stock rights and restricted stock units granted			30	16
Time Vested Restricted Stock [Member]
Share Based Compensation Plans (Textuals) [Abstract]
Restricted stock rights and restricted stock units granted			184	153
Stock Option and Stock Purchase Plan [Member]
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	2,353,000	1,753,000	6,831,000	6,056,000
Nonvested Stock [Member]
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	$ 3,104,000	$ 2,909,000	$ 8,615,000	$ 8,208,000