Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Dividends declared (in dollars per share)	$ 0.25	$ 0.25	$ 0.50	$ 0.50	$ 1.00