Related Party Transactions (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Net expenses from transactions with related parties	$ 1,900,000	$ 2,500,000	$ 3,400,000
Maximum [Member]
Related Party Transaction [Line Items]
Net expenses from transactions with related parties	$ 1,900,000.0	$ 1,900,000.0	$ 2,000,000
Common Stock [Member] | Wilbur L Ross [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners		8.20%	10.20%
Common Stock [Member] | Wellington Management Company LLP [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners	9.30%	6.60%	8.60%