Common Stock - Nonvested Restricted Shares (Details) - Restricted Stock	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Nonvested Restricted Shares
Nonvested, Beginning Balance (in shares) | shares	496,842
Granted (in shares) | shares	347,398
Vested (in shares) | shares	(156,109)
Nonvested, Ending Balance (in shares) | shares	688,131
Weighted Avg. Grant Date Fair Value
Nonvested, Beginning Balance (in dollars per share) | $ / shares	$ 51.65
Granted (in dollars per share) | $ / shares	35.98
Vested (in dollars per share) | $ / shares	46.50
Nonvested, Ending Balance (in dollars per share) | $ / shares	$ 44.90