Basis of Presentation (Details) Share Based Compensation (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013 plan	Sep. 30, 2012	Sep. 30, 2013 plan	Sep. 30, 2012	Dec. 31, 2012
Share-based Compensation
Number of stock-based compensation plans in effect	1		1
Number of shares of issuable common shares (in shares)	2,654,000		2,654,000
Summary of SAR Activity, Other Data:
Outstanding, weighted average contractual term			2 years 8 months 12 days		3 years 6 months
Outstanding and exercisable, weighted average contractual term			2 years 8 months 12 days		3 years 6 months
Deferred Compensation:
Deferred compensation payable	$ 23,802,000		$ 23,802,000		$ 22,607,000
Increase in deferred compensation liability	1,200,000
Increase in fair value of plan assets			1,500,000
Deferred compensation expense	589,000	880,000	1,500,000	2,300,000
RSUs
Share-based Compensation
Stock-based compensation expense	958,000	946,000	2,900,000	2,900,000
Summary of RSU Activity:
Outstanding, beginning of period (in shares)			467,716
Granted (in shares)			15,435
Vested (in shares)			(13,716)
Outstanding, end of period (in shares)	469,435		469,435
Unrecognized compensation cost	4,007,000		4,007,000
Summary of SAR Activity:
Granted (in shares)			15,435
SARs
Share-based Compensation
Stock-based compensation expense			$ 0	$ 0
Number of outstanding awards in-the-money (in shares)	0		0
Summary of RSU Activity:
Granted (in shares)			0	0
Outstanding, end of period (in shares)	0	0	0	0
Summary of SAR Activity:
Outstanding, beginning of period (in shares)			1,812,079
Granted (in shares)			0	0
Expired (in shares)			(195,454)
Exercised in period (in shares)	253,000		0	0
Outstanding and exercisable, end of period (in shares)	1,616,625		1,616,625
Summary of SAR Activity, Other Data:
Weighted average exercise price, outstanding (in dollars per share)			$ 36.16
Weighted average exercise price, outstanding and exercisable (in dollars per share)	$ 36.45		$ 36.45