Consolidated Statements of Shareholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares
Statement of Stockholders' Equity [Abstract]
Common shares repurchased (in shares) | shares	530,882	756,252
Repurchase of common shares, weighted average price (in dollars per share)	$ 59.83	$ 59.76
Stock dividend declared, percent	15.00%
Cash dividend declared - common shares, per share (in dollars per share)	$ 1.08	$ 0.94