Stock-Based Compensation (RSU Activity) (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
RSUs
Number of Shares
Balance at the beginning of the period (in shares) | shares	871,000
Granted (in shares) | shares	523,000
Vested (in shares) | shares	(330,000)
Cancelled (in shares) | shares	(22,000)
Balance at the end of the period (in shares) | shares	1,042,000
Weighted-Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) | $ / shares	$ 28.42
Granted (in dollars per share) | $ / shares	27.88
Vested (in dollars per share) | $ / shares	28.76
Cancelled (in dollars per share) | $ / shares	28.23
Balance at the end of the period (in dollars per share) | $ / shares	$ 28.04
Restricted Stock | Outside directors
Number of Shares
Granted (in shares) | shares	1,700
Weighted-Average Grant Date Fair Value
Granted (in dollars per share) | $ / shares	$ 29.39
Additional Disclosure
Grant-date fair value (in dollars) | $	$ 50,000