Shareholders' Equity Shareholders' Equity - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Feb. 28, 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount	$ 7,000,000	$ 7,000,000	$ 18,000,000
Treasury stock, value		27,637,000
Stock repurchase program, remaining authorized repurchase amount	$ 50,000	$ 50,000
Stock Repurchase Program March 2018
Equity, Class of Treasury Stock [Line Items]
Treasury stock, shares held (in shares)	984,000
Treasury stock, value	$ 7,424,000