Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 15,868	$ 12,434	$ 54,740	$ 47,249
Weighted Average Number of Shares Outstanding, Basic	84,837	85,646	84,799	86,189
Earnings Per Share, Basic	$ 0.19	$ 0.15	$ 0.65	$ 0.55
Dilutive Securities, Effect on Basic Earnings Per Share, Including Options and Restrictive Stock Units	$ 0	$ 0	$ 0	$ 0
Incremental Common Shares Attributable to Share-based Payment Arrangements	201	279	242	319
Weighted Average Number of Shares Outstanding, Diluted	85,038	85,925	85,041	86,508
Earnings Per Share, Diluted	$ 0.19	$ 0.14	$ 0.64	$ 0.55