Quarterly Consolidated Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, 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, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Consolidated Financial Information (Unaudited)
Total revenue	$ 47,203	$ 37,952	$ 37,953	$ 35,304	$ 39,692	$ 37,506	$ 35,153	$ 35,739	$ 37,669	$ 39,480	$ 38,692	$ 40,812	$ 158,412	$ 148,090	$ 156,653
Net income (loss)	6,553	(2,229)	9,692	1,610	2,211	(7,194)	3,229	3,289	3,648	2,316	3,481	5,063	15,626	1,535	14,508
Net income (loss) attributable to common shareholders	$ 6,553	$ (2,229)	$ 9,692	$ 1,610	$ (771)	$ (7,976)	$ 2,447	$ 2,507	$ 2,866	$ 1,534	$ 2,699	$ 4,281	$ 15,626	$ (3,793)	$ 11,380
Basic earnings (loss) per common share (in dollars per share)	$ 0.84	$ (0.29)	$ 1.20	$ 0.20	$ (0.09)	$ (0.94)	$ 0.29	$ 0.30	$ 0.34	$ 0.18	$ 0.33	$ 0.5	$ 1.95	$ (0.45)	$ 1.35
Diluted earnings (loss) per common share (in dollars per share)	$ 0.81	$ (0.28)	$ 1.17	$ 0.19	$ (0.09)	$ (0.91)	$ 0.28	$ 0.29	$ 0.33	$ 0.17	$ 0.31	$ 0.47	$ 1.89	$ (0.43)	$ 1.28
Average common shares outstanding (in shares)	7,846	8,126	8,106	8,033	8,277	8,667	8,585	8,404	8,425	8,397	8,322	8,552	8,029	8,490	8,423
Diluted average common shares outstanding (in shares)	8,084	8,329	8,303	8,273	8,525	8,889	8,848	8,756	8,758	8,811	8,796	9,048	8,289	8,791	8,876