Share-Based Compensation and Equity - Share-based Compensation Expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	$ 13,840	$ 14,296	$ 12,541
Tax benefit	(4,644)	(4,912)	(4,640)
Compensation expense, net of tax	9,196	9,384	7,901
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	2,572	3,486	3,540
Tax benefit	(825)	(1,238)	(1,310)
Compensation expense, net of tax	1,747	2,248	2,230
Restricted Stock Units [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	5,741	5,734	4,355
Tax benefit	(1,809)	(1,845)	(1,611)
Compensation expense, net of tax	3,932	3,889	2,744
Performance Shares [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	4,425	4,076	3,820
Tax benefit	(1,602)	(1,459)	(1,413)
Compensation expense, net of tax	2,823	2,617	2,407
Director Deferred Shares [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	1,102	1,000	826
Tax benefit	(408)	(370)	(306)
Compensation expense, net of tax	$ 694	$ 630	$ 520