Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 18,227	$ 22,532	$ 34,816	$ 37,412
Weighted Average Number of Shares Outstanding, Basic	86,451	90,689	86,463	90,689
Earnings Per Share, Basic	$ 0.21	$ 0.25	$ 0.40	$ 0.41
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	328		339
Net Income (Loss) Available to Common Stockholders, Diluted	$ 18,227		$ 34,816
Weighted Average Number of Shares Outstanding, Diluted	86,779	90,689	86,802	90,689
Earnings Per Share, Diluted	$ 0.21	$ 0.25	$ 0.40	$ 0.41