Subsequent Event (Details) - $ / shares		3 Months Ended
	Apr. 28, 2016	Mar. 31, 2016	Mar. 31, 2015
Subsequent event
Quarterly cash dividends declared to holders of common stock		$ 0.09	$ 0.08
Subsequent events
Subsequent event
Quarterly cash dividends declared to holders of common stock	$ 0.09
Subsequent events | Series C convertible perpetual preferred stock
Subsequent event
Quarterly cash dividends declared to holders of Series C preferred stock (on an as converted basis)	$ 0.09