Shareholders' Equity - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Mar. 11, 2016
Stockholders Equity [Line Items]
Capital conservation buffer rate	1.25%	0.625%
Reclassification adjustment from accumulated other comprehensive loss to retained earnings	$ 8,500
Dividends on common stock [Abstract]
Dividend potential for next fiscal year	$ 87,000
Period for which retained net income considered for approval	2 years
Stock Repurchase Program
Dividends on common stock [Abstract]
Amount of stock authorized for repurchase			$ 100,000
Repurchase shares of common stock	0	34,000
Repurchase shares of common stock, value		$ 750