Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Dividends Declared

					Ordinary Dividends
Declaration Date	Payment Date	Record Date	Distribution Per Share		Qualified (1)		Non-Qualified		Nondividend Distributions (2)		Aggregate Payment Amount (millions)
January 17, 2013	March 1, 2013	February 15, 2013	$	0.50	$	0.1551057	$	0.3448943	—		$	35.7
May 7, 2013	June 3, 2013	May 20, 2013	$	0.50	$	0.1551057	$	0.3448943	—		$	35.8
July 30, 2013	August 29, 2013	August 19, 2013	$	0.50	$	0.1551057	$	0.3448943	—		$	36.1
November 1, 2013	November 26, 2013	November 14, 2013	$	0.55	$	0.1706163	$	0.3793837	—		$	39.6
February 18, 2014	March 14, 2014	March 3, 2014	$	0.57	$	0.0448272	$	0.4154156	$	0.1097572	$	41.1
April 28, 2014	May 27, 2014	May 15, 2014	$	0.57	$	0.0448272	$	0.4154156	$	0.1097572	$	41.5
August 5, 2014	August 29, 2014	August 18, 2014	$	0.57	$	0.0448272	$	0.4154156	$	0.1097572	$	41.4
November 5, 2014	November 26, 2014	November 17, 2014	$	0.62	$	0.0487594	$	0.4518556	$	0.1193850	$	46.0
February 6, 2015	February 27, 2015	February 17, 2015	$	0.62	$	0.0529749	$	0.4139721	$	0.1530530	$	46.0
April 29, 2015	May 21, 2015	May 11, 2015	$	0.62	$	0.0529749	$	0.4139721	$	0.1530503	$	46.3
July 31, 2015	August 24, 2015	August 14, 2015	$	0.62	$	0.0529749	$	0.4139721	$	0.1530530	$	46.3
November 3, 2015	November 25, 2015	November 16, 2015	$	0.65	$	0.0555382	$	0.434003	$	0.1604588	$	48.5