Shareholders' Equity Shareholders' Equity - Additional Information (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Feb. 28, 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount	$ 7,000	$ 18,000
Treasury stock, value	20,212
Stock Repurchase Program, Remaining Authorized Repurchase Amount	7,425
Stock Repurchase Program March 2018 [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount	$ 50,000
Treasury stock, shares held (in shares)	2,307
Treasury stock, value	$ 20,212