Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 12,434	$ 15,399	$ 47,249	$ 52,810
Weighted Average Number of Shares Outstanding, Basic	85,646	90,129	86,189	90,500
Earnings Per Share, Basic	$ 0.15	$ 0.17	$ 0.55	$ 0.58
Dilutive Securities, Effect on Basic Earnings Per Share, Including Options and Restrictive Stock Units	0		0
Incremental Common Shares Attributable to Share-based Payment Arrangements	279		319
Net Income (Loss) Available to Common Stockholders, Diluted	$ 12,434		$ 47,249
Weighted Average Number of Shares Outstanding, Diluted	85,925	90,129	86,508	90,500
Earnings Per Share, Diluted	$ 0.14	$ 0.17	$ 0.55	$ 0.58