Summary of Operations and Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share [Abstract]
Options and share outstanding									2,000,000	2,000,000	3,000,000
Earnings Per Share Reconciliation [Abstract]
Weighted average number of common shares outstanding used in computing basic earnings per share									45,202,000	44,146,000	42,237,000
Net income attributable to common stockholders	$ 3,115	$ 9,957	$ 17,981	$ 19,684	$ 23,967	$ 21,162	$ 16,647	$ 14,958	$ 50,737	$ 76,733	$ 7,513
Basic earnings per share attributable to common stockholders	$ 0.07	$ 0.22	$ 0.38	$ 0.44	$ 0.54	$ 0.48	$ 0.38	$ 0.34	$ 1.12	$ 1.74	$ 0.18