Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Total gross revenues	$ 102,169	$ 97,689	$ 95,684	$ 96,099	$ 95,326	$ 105,981	$ 116,912	$ 111,277	$ 391,641	$ 429,496	$ 430,839
Net income (loss)	31,448	5,596	7,365	42,220	16,929	(27,612)	56,680	50,453	86,629	96,450	114,891
Net income attributable to common shareholders	$ 29,235	$ 3,916	$ 5,519	$ 40,397	$ 14,391	$ (26,975)	$ 53,875	$ 47,781	$ 85,583	$ 95,624	$ 111,703
Net income attributable to common shareholders - basic (in dollars per share)	$ 0.12	$ 0.02	$ 0.02	$ 0.17	$ 0.06	$ (0.12)	$ 0.23	$ 0.21	$ 0.33	$ 0.38	$ 0.45
Net income (loss) attributable to common shareholders - diluted (usd per share)	$ 0.12	$ 0.02	$ 0.02	$ 0.17	$ 0.06	$ (0.12)	$ 0.23	$ 0.20	$ 0.33	$ 0.37	$ 0.45
LCIF [Member]
Condensed Income Statements, Captions [Line Items]
Total gross revenues	$ 21,604	$ 21,242	$ 20,646	$ 19,281	$ 18,739	$ 30,558	$ 40,772	$ 34,100	$ 82,773	$ 124,169	$ 128,001
Net income (loss)	$ 8,459	$ (4,422)	$ (8)	$ (470)	$ 16,877	$ (61,579)	$ 22,754	$ 18,027	$ 3,559	$ (3,921)	$ 42,315
Net income (loss) (usd per unit)	$ 0.11	$ (0.05)	$ 0.00	$ (0.01)	$ 0.20	$ (0.74)	$ 0.27	$ 0.22	$ 0.04	$ (0.05)	$ 0.58