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, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Options and share outstanding									2	2	2
Earnings Per Share Reconciliation [Abstract]
Weighted average number of common shares outstanding used in computing basic earnings per share									45,780,000	45,202,000	44,146,000
Net income attributable to common stockholders	$ 4,075	$ 8,553	$ 6,653	$ 4,871	$ 3,115	$ 9,957	$ 17,981	$ 19,684	$ 24,152	$ 50,737	$ 76,733
Basic earnings per share attributable to common stockholders	$ 0.09	$ 0.19	$ 0.15	$ 0.11	$ 0.07	$ 0.22	$ 0.38	$ 0.44	$ 0.53	$ 1.12	$ 1.74