Related Party Transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 08, 2016	Apr. 01, 2016	Mar. 31, 2016
Related Party and Similar Transactions
Repurchased price				$ 24.95		$ 21.59
Number of shares repurchased				$ 40,000
Percentage of difference in repurchase and closing price				2.00%
Closing price				$ 25.46
WMES | Other Revenue
Related Party and Similar Transactions
Asset Management Fees	$ 2,100,000	$ 1,700,000	$ 2,000,000
Chief Executive Officer [Member]
Related Party and Similar Transactions
Number of shares repurchased					$ 60,000