Earnings Per Share - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic Earnings per Common Share
Net income attributable to Company	$ 29,694	$ 14,336	$ 59,311	$ 33,517
Less: Preferred stock dividends	(5,925)	(3,225)	(11,850)	(6,450)
NET INCOME ATTRIBUTABLE TO COMPANY'S COMMON STOCKHOLDERS	$ 23,769	$ 11,111	$ 47,461	$ 27,067
Weighted average common shares outstanding-basic (in shares)	115,211	111,863	113,623	111,792
Basic Earnings per Common Share (in dollars per share)	$ 0.21	$ 0.10	$ 0.42	$ 0.24
Diluted Earnings per Common Share:
Net income attributable to Company	$ 29,694	$ 14,336	$ 59,311	$ 33,517
Less: Preferred stock dividends	(5,925)	(3,225)	(11,850)	(6,450)
Add back: Interest expense on convertible notes for the period, net of tax	2,633	0	5,267	0
Net income attributable to Company's common stockholders	$ 26,402	$ 11,111	$ 52,728	$ 27,067
Weighted average common shares outstanding-basic (in shares)	115,211	111,863	113,623	111,792
Net effect of assumed PSUs vested (in shares)	258	0	152	0
Net effect of assumed convertible notes conversion to common shares (in shares)	19,695	0	19,695	0
Diluted weighted average common shares outstanding (in shares)	135,164	111,863	133,470	111,792
Diluted Earnings per Common Share (in dollars per share)	$ 0.20	$ 0.10	$ 0.40	$ 0.24