Shareholders' Equity (Details) - USD ($)			3 Months Ended
	Mar. 29, 2018	Mar. 15, 2018	Mar. 31, 2018	Mar. 31, 2017	Nov. 10, 2017
Class of Stock [Line Items]
Dividends declared per common share (in dollars per share)			$ 0.33	$ 0.32
Dividends declared and paid, preference shares			$ 5,595,000	$ 5,595,000
Retained Earnings
Class of Stock [Line Items]
Dividends declared and paid, preference shares			5,595,000	5,595,000
Dividends declared and paid, common shares			13,224,000	$ 13,027,000
Common Shares
Class of Stock [Line Items]
Dividends declared per common share (in dollars per share)		$ 0.33
Dividends paid per common share (in dollars per share)	$ 0.33
Share repurchase program, authorized amount					$ 500,000,000
Share repurchase program, remaining authorized aggregate amount			$ 500,000,000
Series C Preference Shares
Class of Stock [Line Items]
Dividend rate, percentage			6.08%
Liquidation preference per annum (in dollars per share)			$ 1.52
Liquidation preference quarterly (in dollars per share)			$ 0.38
Series E Preference Shares
Class of Stock [Line Items]
Dividend rate, percentage			5.375%
Liquidation preference per annum (in dollars per share)			$ 1.34375
Liquidation preference quarterly (in dollars per share)			$ 0.3359375