CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (Parenthetical)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Series D Preferred Stock [Member]
Preferred stock dividend (in percent)	9.00%	9.00%	9.09%

The percentage rate used to calculate dividend payments on preferred stock.

No definition available.

Name:	us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration