Subsequent Events - Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity
Dividends per share declared (in dollars per share)		$ 0.54	$ 0.51	$ 1.08	$ 1.02
Net proceeds				$ 70,885
Common Stock | Equity Distribution Agreement
Equity
Issuance of common stock (in shares)				1,490,394
Net proceeds				$ 70,885
Amount available under effective shelf registration statement		$ 127,853		$ 127,853
Subsequent Event | Common Stock | Equity Distribution Agreement
Equity
Issuance of common stock (in shares)	152,623
Net proceeds	$ 7,715
Amount available under effective shelf registration statement	$ 120,000
Dividend Payable, July 29, 2016 | Subsequent Event
Equity
Dividends per share declared (in dollars per share)	$ 0.18
Dividend Payable, August 31, 2016 | Subsequent Event
Equity
Dividends per share declared (in dollars per share)	0.18
Dividend Payable, September 30, 2016 | Subsequent Event
Equity
Dividends per share declared (in dollars per share)	$ 0.18