Consolidated Statements of Changes in Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Stockholders' Equity [Abstract]
Common dividends declared per share (in dollars per share)	$ 0.75	$ 0.6375	$ 0.375
Preferred dividends declared per share (in dollars per share)	$ 0	$ 0.63	$ 2.00
Convertible preferred dividends declared per share (in dollars per share)	$ 0	$ 0	$ 0.075
Shares issued in lieu of Directors' fees (in shares)	16,481	11,432	26,047
Issuance of shares pursuant to the TPG Management Services Agreement (in shares)	19,122	26,098	18,399
Issuance of common stock (in shares)	23,716,900	31,049,976	18,951,700
Shares of convertible preferred stock converted to common stock (in shares)	0	0	13,484,444
Shares of restricted stock withheld to satisfy tax withholding obligations on vesting of restricted stock (in shares)	0	3,365	12,169
Distribution of shares of common stock from deferred compensation plan (in shares)		0	12,089
Contribution of shares of common stock to deferred compensation plan (in shares)		0	3,721
Issuance of operating partnership units (in shares)	85,649	5,351,461	1,800,000
Number of share of common stock issued upon redemption of operating partnership units	0	238,357	1,800,000
Limited voting stock, shares issued (in shares)		4,451,461