Share-Based Compensation Plans (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	$ 5,131,000	$ 4,992,000	$ 9,989,000	$ 9,602,000
Income tax benefit	(1,713,000)	(1,640,000)	(3,389,000)	(3,327,000)
Share-based compensation expense, net of tax	3,418,000	3,352,000	6,600,000	6,275,000
Summary of compensation expense recognized related to cash awards
Cash awards	743,000	889,000	1,266,000	2,163,000
Share Based Compensation Plans (Textuals) [Abstract]
Stock option plan granted			405,000	381,000
Total unrecognized pre-tax compensation expense	33,400,000		33,400,000
Unrecognized Compensation Costs weighted-average period (in years)			1 year 11 months 20 days
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period			615,000	564,000
Stock Option and Stock Purchase Plan [Member]
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	2,241,000	2,193,000	4,478,000	4,303,000
Nonvested Stock [Member]
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	$ 2,890,000	$ 2,799,000	$ 5,511,000	$ 5,299,000
Market-based restricted stock rights [Member]
Share Based Compensation Plans (Textuals) [Abstract]
Restricted stock rights and restricted stock units granted			22,000	22,000
Time Vested Restricted Stock [Member]
Share Based Compensation Plans (Textuals) [Abstract]
Restricted stock rights and restricted stock units granted			158,000	146,000
Performance based restricted stock [Member]
Share Based Compensation Plans (Textuals) [Abstract]
Restricted stock rights and restricted stock units granted			30,000	15,000