Equity Compensation Plans - Deferred Stock Units Activity (Details) - Deferred Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Units
Outstanding at beginning of period (in shares)	2,407,154	2,168,824	2,266,473
Granted (in shares)	565,061	583,958	350,769
Distributions (in shares)	(1,060,459)	(335,461)	(440,548)
Forfeited (in shares)	(62,894)	(10,167)	(7,870)
Balance at End of Period (in shares)	1,848,862	2,407,154	2,168,824
Weighted Average Grant Date Fair Market Value
Outstanding at beginning of period (in dollars per share)	$ 16.45	$ 16.20	$ 15.41
Granted (in dollars per share)	13.33	16.11	19.62
Vested (in dollars per share)	14.64	14.20	14.82
Forfeited (in dollars per share)	18.66	16.60	19.06
Balance at End of Period (in dollars per share)	$ 16.46	$ 16.45	$ 16.20