Common Share Capitalization (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended		32 Months Ended
	Aug. 04, 2011	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Common Stock Capitalization [Line Items]
Common Shares Issued And Outstanding Upon Conversion of All Convertible Securities		26,064,802	21,012,819	26,064,802
Shareholders Equity Per Share Upon Conversion Of All Convertible Units (in usd per share)		$ 24.10	$ 24.78	$ 24.10
Dividends (in usd per share)		$ 0.77	$ 1.52
Payments of Dividends		$ (20,070,000)	$ (31,939,000)
Aggregate cost of shares repurchase	10,000,000
Shares repurchased				(217,619)
Aggregate cost of shares repurchased				$ 4,500,000
Average price per share repurchased (in usd per share)				$ 20.59
Regular Dividend [Member]
Common Stock Capitalization [Line Items]
Dividends (in usd per share)			$ 0.77
Special Dividend [Member]
Common Stock Capitalization [Line Items]
Dividends (in usd per share)			$ 0.75