Common Stock and Dividends (Details) - USD ($)						1 Months Ended	3 Months Ended
	May 04, 2018	Apr. 16, 2018	Oct. 16, 2017	Apr. 17, 2017	Apr. 09, 2017	Apr. 30, 2009	Mar. 31, 2018	Apr. 03, 2018
Common Stock and Dividends
Warrants to purchase entity's common stock (in shares)							1,326,238
Warrants, exercise price (in dollars per share)							$ 24.43
Warrants, term							10 years
Maximum cash dividend paid in semi-annual period (in dollars per share)							$ 0.33
Cash dividends paid to common shareholders (in dollars per share)		$ 0.33	$ 0.33	$ 0.33
Repurchase of common stock, authorized amount						$ 40,000,000		$ 40,000,000
Period of repurchase of common stock					12 months	12 months
Cumulative number of shares repurchased under all stock repurchase programs	9,245,658
Cumulative cost of shares repurchased under all stock repurchase programs	$ 271,289,000