Basis of Presentation (Details) Share Based Compensation (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 plan	Jun. 30, 2012	Jun. 30, 2013 plan	Jun. 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	2,654,000		2,654,000
Summary of SAR Activity, Other Data:
Outstanding, weighted average contractual term			2 years 10 months 24 days		3 years 6 months 0 days
Outstanding and exercisable, weighted average contractual term			2 years 10 months 24 days		3 years 6 months 0 days
Deferred Compensation:
Deferred compensation payable	$ 23,213		$ 23,213		$ 22,607
Increase in deferred compensation liability	606
Increase in fair value of plan assets			867
Deferred compensation expense	249	(127)	867	1,500
RSUs
Share-based Compensation
Stock-based compensation expense	950	920	1,900	2,000
Summary of RSU Activity:
Outstanding, beginning of period			467,716
Granted			15,435
Vested			(11,430)
Outstanding, end of period	471,721		471,721
Unrecognized compensation cost	4,965		4,965
Summary of SAR Activity:
Granted			15,435
SARs
Share-based Compensation
Stock-based compensation expense			$ 0	$ 0
Number of outstanding awards in-the-money	0		0
Summary of RSU Activity:
Granted			0	0
Outstanding, end of period	0	0	0	0
Summary of SAR Activity:
Outstanding, beginning of period			1,812,079
Granted			0	0
Expired			(195,454)
Exercised in period			0	0
Outstanding and exercisable, end of period	1,616,625		1,616,625
Summary of SAR Activity, Other Data:
Weighted average exercise price, outstanding			$ 36.16
Weighted average exercise price, outstanding and exercisable	$ 36.45		$ 36.45