Summary of Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income attributed to:
Net income	$ 9,081	$ 15,300	$ 12,072	$ 14,898	$ 15,790	$ 9,413	$ 11,870	$ 11,806	$ 51,351	$ 48,879	$ 42,282
Common Stock
Net income attributed to:
Net income									51,351	48,853	42,040
Participating common restricted stock
Net income attributed to:
Net income										$ 26	$ 242